There's tonnes of free games out there. Most of them are really really bad. Let's synopsise them!
Vitenka has a very clear view of what makes a good game. It's one he likes. On with the show!
This page seems like a good place to list good games. More specifically, since ToothyWikizens' opinions vary, games that at least one ToothyWikizen wants to recommend. I (AlexChurchill) have often wished for a place more specific to games than SiteOfTheMoment, where a number of such games have been linked before but get lost among random other sites, and more specific than CategoryComputerGames, which is mostly ones requiring a specific platform or console.
As much as is possible, let's try to sort them by genre. Let's also include who recommended them. In some cases this has been copied from the mention on SiteOfTheMoment or another wiki page.
Probably ought to mention the massive glut of 'pay for items' so-called korean style, so called 'free to play' games. All much of a muchness, so I may as well link the grandaddy [A Perfect World]. (It's.. not terrible. Questy, which is a nice change.)
AnarchyOnline. Almost the only surviving sci-fi game out there that isn't gorramit Eve. (Ok, there's dome of york, but that has no free version and despite the fps element, is dull.) Whole game plus first expansion free, subscribe if you want more. Stupidly complex, yet lacking much beyond 'whack a rat'.
http://www.animecubed.com/billy/?116838 - Billy vs. SNAKEMAN. I just discovered this the other day (yes, that comment will become dated fast), and it's an anime-parodying browser MMO based primarily on Naruto. A little like Kingdom of Loathing, in a way, and pretty good fun. Recommended by Anonyman.
[D&D Online] (Eberron Unlimited) - the official MMO for Dungeons and Dragons; free to play with minor restrictions on choice of class and race, which are liftable by micropayment or by accruing "favour" points through your free chars. ChrisHowlett is enamoured at present (and Vitenka seems to be somewhat).
Single-player
Tower Defence
/TowerDefence is a genre that originated in custom maps for WarCraft III, but rapidly migrated to Flash games, where it's become spectacularly successful.
[Gemcraft] has a nice campaign mode. (Recommended by Vitenka, AlexChurchill) And a [prequel], now, with even more reasons to replay the same levels. Swarm mode is fun. (Recommended by AlexChurchill)
[Protector III] also has an ongoing campaign, including persistent "hero" units who level up across multiple maps. (Recommended by AlexChurchill)
Somewhere between Tower Defence and RTS comes [The Space Game], where you have to build buildings, mine minerals, route power networks, and build laser and missile emplacements to fight off the waves of pirate ships. (Recommended by AlexChurchill)
And now there's an [expansion] for it, where you get more interesting mission-based gameplay. (Highly recommended by AlexChurchill)
And somewhere between Tower Defence and shoot-em-up comes [Storm Winds], a tower defence game where you have to direct all the shooting, which makes it feel more like a shoot-em-up with a static player sprite, but lots of choices of turrets and upgrades in the usual fashion. (Recommended by AlexChurchill)
[Creeper World] is not free but the online demo / [training sim] is. Towers vs. a liquid ooze rather than distinct enemies. Kazuhiko found it interesting.
Continuing the trend of odd semi-defence hybrid games is [CellCraft], a game of defence and resource management where you have to balance your consumption of different resources such as ATP, glucose, and nucleic acids, and vigorously defend your cell from invaders and infesters, using lysosomes, slicer enzymes and defensins. And also help space-travelling platypuses. (Recommended by AlexChurchill)
[ElectroCity] is a SimCity-style game of managing a city's growth through 150 turns, trying to keep on top of energy, pollution, money and public opinion. (Recommended by AlexChurchill)
[Spitfire: 1940] Fight the Battle of Britain (only from the British side). Balance the demand for fighters, pilots and keeping the cities standing, and then let the Germans bomb London because there's a slight threat to your radar stations which are clearly more important. Recommended by StuartFraser.
Shoot-em-up
[Canary] is by Nitrome, makers of lots of fun browser games. This one's a side-scrolling shooter where you play as a canary with a mining laser. (Recommended by AlexChurchill)
WarningForever is a free ShootEmUp for Windows with its own wiki page. (Recommended by Vitenka, Kazuhiko and Xarak, going by that page)
Programming
TheCodexOfAlchemicalEngineering? is what happens when alchemy meets programming meets flash game. (Recommended by AlexChurchill)
[LightBot] - Program the bot to light the blue squares. The difficulty curve can be roughly described as an open field with a cliff face (level 10) on one end. Levels 11 & 12 are tricky but not as hard as 10. (Recommended by Kazuhiko)
Physics
FantasticContraption is an awesome game of building machines to solve challenges in a 2D physics engine.
/BridgeBuilder (a game in which you build bridges. And watch them fall down.) has a few others. (Recommended by Vitenka)*
[Wake Up The Box] is a physics puzzle game where you have to nudge, jiggle or shake a sleeping cardboard box, using balance and centres of gravity and suchlike. (Recommended by AlexChurchill)
Click-and-shoot
There are a number of games in this genre, vaguely similar to PuzzleBobble?.
[Peggle] Sort of halfway between PuzzleBobble? and pinball. Recommended by Rachael.*
[Keggle] is an alternative for those who prefer Java. It was an entry in the Java 4k competition 2009. (Recommended by PeterTaylor)
Platform
A number of FunOrb games are platformers and have large free sections. Most notably, [Miner Disturbance] is a game of digging into a volcano which is now free to play. (Recommended by AlexChurchill)
[Fold] - a platform game where you manipulate gravity. (Recommended by qqzm and AlexChurchill)
[Lost in the Static]: a platform/exploration game (perfectly playable), but each screenshot is a field of random static.
/Nifflas(Knytt, WithinADeepForest??; Recommended by Vitenka)
[Chronotron] is an interesting time-travelling platform game. You can go back in time, effectively spawning an extra copy of yourself, who can cooperate with you, e.g. holding down buttons so you can go through doors - but obviously old-you will only do the actions you did before you went in the time machine. Recommended by AlexChurchill and Rachael.
[Super Mario Sunshine] - A remarkably good 2D homage to the 3D Mario games Mario64 and Mario Sunshine. Four main worlds, each with (at least) 3 stars to earn, classic 2D Mario gameplay and enemies with a slight Mario Sunshine flavour, and a good helping of secrets. Unfortunately it glitches if you leave the quality too high, but apart from that, distinctly recommended by AlexChurchill to anyone who appreciated Mario in his 2D and 3D incarnations. (Changed the link to a version that should be less glitchy and that saves your progress)
Actually, forget that one, just play [Super Mario Sunshine 63]. Even more worlds, even better castle with secrets galore, more puzzles with 3 different FLUDDs, and far fewer glitches. (Recommended by AlexChurchill)
Iji, by Daniel Remar [1]. Reviewed by AlexChurchill in more depth [here]. An excellent platform shooter, or perhaps a platform puzzler disguised as a platform shooter. A very difficult game with an excellent branching storyline. Beating the game without killing a single enemy is possible and significantly changes the ending. The author described it as a platforming version of System Shock's gameplay; excellent. Windows application. (Recommended by ElliottBelser and AlexChurchill)
The Mighty Jill-Off [2]. Not safe for work. Or possibly your mind. A "masocore" platformer which takes the masochistic subtext of games like I Wanna Be The Guy and turns it into, er, text, in a way that comes off as cute and affectionate rather than Just Plain Creepy. Windows application. I recommend Dessgeega's other games as well. (Recommended by ElliottBelser)
Raider, [episode 1] and [episode 2]. A good old-school hardcore platformer. A GenreSavvy? protagonist, four secrets per episode (sometimes evilly tricky), a potentially-interesting plot split across 5 episodes, and some crazy-difficult jumping, particularly in the second half of episode 2. When it recommends you play on Beginner difficulty till you've completed it once, it's not joking. (Recommended by AlexChurchill)
[Finwick], a pleasingly smooth puzzle platformer. Guide Finwick, working as a postman in his summer holidays, as he braves thousand-volt plasma, murderous beasts, and lots of switches and platforms, because the mail must get through! (Recommended by AlexChurchill. Note the first 25 levels are free, which is quite a sizeable chunk; after that costs $6.)
[Parasite]. A brightly coloured world with flying fluffy kittens, cute butterflies, and sparkling purple "happy gas". Enslave and conquer it all with your GasGuzzler? 9000 (but it stays just as brightly-coloured even when you conquer it, though the creatures do develop green drool). A collection of 20 puzzlish-platform levels, which start off pretty gentle but get quite tricky around 9-10. Level 15 (the one with a slight Portal reference) is particularly good. (Recommended by AlexChurchill)
[Robot Wants Kitty]. A pleasing little 15-minute Metroidvania. Guide the robot round the single large level, acquiring powerups to get to new areas. (Recommended by AlexChurchill and PeterTaylor)
[Redder]. Nonlinear platform puzzling at its purest. Well, okay, not quite as pure as Knytt, but that was "pure" enough for AC to find it just dull. Redder adds just one thing - red blocks and green blocks, which are either solid or passable depending on whether the most recent switch you pressed was red or green - but that, in the setting of exploring a big world collecting items as you go, is enough for some excellent puzzles with a good difficulty curve. (Recommended by AlexChurchill)
Note: Alex described this as "platform puzzling at its purest". If you misread this (as I did) as saying it's a pure puzzle game you will be very disappointed. --PT
[Pieces]. Thoroughly in the MetroidVania mould, this: explore a big nonlinear world in whatever order you want, gaining skills that let you reach new places. The twist is that gaining skills has two parts: first Proo needs to realise she needs some skill, then she needs to watch an animal to obtain that skill. And sometimes the spots to trigger her realising she needs a skill are not in the most obvious places. But nonetheless, it's a pleasingly large world with a lot of areas to explore, a lot of gems to collect, and a lot of fun to be had. (Recommended by AlexChurchill)
You /can/ explore it in whatever order you want, but if you don't pick the right order you risk getting stuck in a dead end. --PT
[Sky Island] - If you remember Fez, the perspective-switching game from a few years ago that never got released: this is the same thing, but playable in Flash. If you don't: imagine a 2D platformer, but if you drag the mouse, it reveals that you're actually playing on one of four views of a 3D landscape (from the north, south, east or west). The twist is that the dimension you can't see is collapsed: so you can step from one block to a neighbouring block, then rotate the view and discover you've stepped twenty blocks' distance in the dimension that was previously collapsed. A variety of nifty puzzles emerge from this principle. (Recommended by AlexChurchill)
Puzzle
[Evacuation] - puzzle game to eject aliens into space by toggling groups of airlock doors. It's quite unforgiving: let just one of the red-suited guys (officers) die and that's game over: although you can replay the level you died on unlimited times, you can't progress any further, and have to restart from level one if you want to progress further. AlexChurchill's highscore is 512, which was around level 17 or so. (Recommended by AlexChurchill)
[Grid] - rotate sections of pipe to form a complete grid, but only ones that have power. AlexChurchill finished it in the end, with a score of 67852. (Recommended by AlexChurchill)
And there's now a sequel, [Grid 2], which keeps the same basic idea but adds a few slight twists for 40 more levels of puzzling fun. AlexChurchill scored 130100 by the end. (Recommended by AlexChurchill)
[Putty Shuffle] - by the same designer as Putty Puzzle, although shorter because it was a Java4k entry. (Recommended by PeterTaylor)
[Planarity] - a distressingly addictive game; simply drag the vertices to make the graph planar (no overlapping edges). Really not very easy.
[Hapland] - in the subgenre of games where you have a detailed landscape and some things to click. This one has a variety of stick figures strewn around. (Recommended by AlexChurchill)
[Chromatron] - fire beams of coloured light into mirrors, prisms, quantum splitters, etc. Like Reflexion but more complicated/interesting. Recommended by AlexChurchill and Rachael.
[Prism - Light The Way] - Quite similar to Chromatron: direct the light beams to the requisite coloured targets, using prisms and suchlike. Turn the quality down to low to get better responsiveness. Some of the puzzles are rather tricky. (Recommended by AlexChurchill)
ElectricBox - In order to get electric power from the source to the target, you'll have to convert it to and from laser light, visible light, steam power, water power, air power, and use robots and destructive balls to change your circuits on the fly. Once you've solved the 15 built-in levels, there are 30 more [here]. (Recommended by AlexChurchill)
[Neon Maze] - A maze built of walls of six different colours; your ship can travel through the walls of its colour. 20-something levels. Quite fun. (Recommended by AlexChurchill)
[PLANned] - A simple puzzle game of choosing the right order to expand the right squares. Click a square to expand it, but only if it's not connected to another, or been expanded 3 times, or the last one you clicked; link everything into one network (connected at corners) to pass the level. (Recommended by AlexChurchill)
[CiviBalls 2] - A puzzle physics game. The levels have been carefully set up so that breaking the few chains, in the right order and with the right timing, will allow each coloured ball to be delivered to the corresponding coloured pot. They get impressively tricky quite quickly. (Recommended by AlexChurchill)
[The Wizard's Notebook] - A quick and charming little game where you can type text into spaces to summon certain items. The fun comes because the game hasn't told you what words will "come to life" as it puts it - you just have to figure it out based on the level designs (though the level titles are often pretty big hints). Only 11 levels, but a nice concept. (Recommended by AlexChurchill)
[Escape] - A tile-based, turn-based puzzle game with the simple objective of reaching the goal square without dying. It goes without saying that different levels add different kinds of obstacles to stop you from doing so (from typical block-pushing levels all the way up to one level that forces you to crack a DES-like cipher to open the goal). Over 2,500 user-submitted levels, and the game's philosophy is such that it should be easy (and encouraged) to add your own to the collection. (Recommended by SadisticMystic)
[Isoball 2] - Place blocks in a small isometric space to enable a ball to roll from the entry to the exit. Sounds straightforward? It gets extremely tricky when your quantities of each of several type of block are restricted, and the level has random holes in which you have to use up your precious bridges on, and... 50 levels, which start off pretty easy but by 20-25 are getting very hard. CategoryTimeSink warning. (Recommended by AlexChurchill)
[Exploit], a hacking-themed game where you fire packets into networks to overflow buffers, disable latch nodes, and rebound around ports to eventually get to the root node. Fun storyline mode and 19 challenge puzzles too. (Recommended by AlexChurchill)
Reflexes
[Red Square] - move the red square to stay away from the blue squares. Playing time of 16-20 seconds.
[Russian flash game] - Click on the top one of the three options towards the bottom of the right-hand side to start playing. Pull on the tails of the rodent things hanging down in the middle to set them swinging, then get the guy to pull on the tail of the thing on the left to get it to spit out a balloon; you're trying to time the balloon to not hit any of the swinging things so the weird elephant creature on the right swallows it.
[Ladybug] - Lead the Ladybug around the maze of twisty passages without letting it bump its nose. Very simple, but very, very hard to complete...
/Armagetron (racing light cycles; Recommended by Vitenka)''*
[Ragdoll Avalanche 2] - cursor keys control the head, the rest of the ragdoll follows, and you can only get away with losing the arms below the elbow and the legs below the knees. (Recommended by PeterTaylor)
[Santa Rockstar] - It's Guitar Hero. In Flash. Playing (electric guitar arrangements of) Christmas songs. (Recommended by StuartFraser)
If the city is too exciting, you can always play [Desert Bus].
[Genetos] - a quick run through of the history of SHUMPs.
[Oolite] Object Oriented (e)lite. A pretty faithful adaptation of Elite, but fully rendered and textured, with an easily modded system. Lots of mods appear to exist. Finding the controls is probably the first issue, but you can get the info off the wiki if you look hard.
KatawaShoujo? - A free slice-of-life RenAi game about a boy with a heart murmur, sent to an academy for the deaf, blind and otherwise physically disabled in Japan: he then meets five rather attractive young women and begins to fall in love and get on with his life. Bar none the best depiction of life with disabilities that ElliottBelser has ever seen, in any medium. Started life as a bit of fanart that became inexplicably popular on 4Chan, then spun off into an amateur game company, Four-Leaf Studios. Note that it's the first act of what will eventually be a Hentai? game (Act 1 is something I wouldn't mind showing a 13 year old, though); the full version, with sex scenes, will be free as well. - Recommended by ElliottBelser
Interactive Fiction
There's a whole genre of InteractiveFiction (aka text adventures), older than most genres of computer game. But a number are now playable on the web, which makes it hard to decide whether they belong on this page or that. AlexChurchill will list some of his favourites here.
[Violet], a single-room IF game about procrastination. It's got a great twist on the usual IF second-person description: it's still second-person, but the speaker is the protagonist's girlfriend - or rather, his imaginary version of her. The backstory of their relationship (and the characters' previous relationships) is narrated via reminiscence over the course of the game. You could treat this game as a fascinating take on a [[ren'ai]] IF game, or just as a straight IF puzzle game, according to your preferences.
[Suveh Nux], a single-room IF game with a fascinating magic language. The first 95% of the game is fairly easy, including finishing it. The final 5% is Easter eggs which are quite a bit tougher, but very clever.
[Bastet] - A version of Tetris that figures out what block you most need, and gives you anything but that one.
[Achievement Unlocked] and [Upgrade Complete] - a pair of games spoofing the current obsession with achievements and upgrades. The splash screen is, well, an achievement in one and an upgrade in the other. Both are quite fun. (Recommended by AlexChurchill)
Heh. I indeed guessed correctly the 'twist' in upgrade-complete. And am still playing on because it's actually quite mindlessly fun. --Vitenka
A word for the puzzled and frustrated: when you purchase the pre-loader in Upgrade Complete it should immediately execute it. However, it you have a version of Flash earlier than 10 it will fail silently, and the first thing you must upgrade is your Flash plugin. --PT
[You Have to Burn the Rope] was a finalist for the IGF? "Innovation" award. Clearly the judges have a sense of humour. It directly spoofs Shadow of the Colossus and indirectly the whole concept of modern game bosses. (Recommended by PeterTaylor)
[G-E-N-E-R-I-C]. A puzzle platformer with a twist. If you can't figure out the twist (and thus get beyond level 4 or so), the readme file has a big hint. Windows, runs in a window. (Recommended by AlexChurchill)
[Trackmania Nations Forever] A near-commercial quality racing game, with lots of jumps and wall-running in the style of the old StuntCarRacer?. Large parts of the time SF is supposed to be spending writing job applications and going over thesis are being spent playing Trackmania. StuartFraser would love to have ToothyWikizens to race against.
Word
[Wordspector] - a pleasing version of Mastermind, where your target and submissions have to be dictionary words. Starts off at 4 letters which is nice and easy, but AC finds 6 letters extremely difficult. (Recommended by AlexChurchill)
A hybrid of (of all things) the physics and word puzzle genres is [Prose and Motion]. You're given a bunch of letters, and sometimes other blocks. You have to move them around to form a word, starting in a specified zone. All objects move under physics: the letters fall over or be rotated. Each level has one word that is the "perfect" one for you to form, and spotting that anagram can be quite tricky, when there are two blocks which could be E, M or W depending on how you orient them... It manages a challenge that I wouldn't have ever thought of, which is to make a puzzle game that's got genuine physics puzzle elements and genuine word puzzle elements. (Recommended by AlexChurchill)
[Scribble] - a Scrabble variant where everyone's on the same team and uses the same rack. There are also 10 tiles on that rack, so needless to say there's a lot more building up to triple-triples (just beware of the mischievous users who try to claim the triple spots with low-scoring words). You can add six more "advanced" tables to the list by adding "?flags=debug" to the URL -- these tables are hidden by default so as to be less susceptible to wandering newcomers messing up the board position.
Miscellaneous
There are some BrowserGames? that defy categorisation.
[Cat on a Dolphin] - (Brief explanation: One button game. Hold the button to accelerate (with cat attached). Release the button to release the cat. Use this to launch the cat out of the water so it can breathe but make sure you catch up to it before it falls)
[Minecraft] - a sandbox building game with great multiplayer (although there are some rather nasty people around) and which has great potential for the future - the creator is working on a single-player adventure/RPG mode.
Just spent (too many) pleasant hours fixing underwater tunnels to be water tight. Very much panders to the obsessive compulsive. Very pretty in its own way. Enjoy while you can since, IMHO, this is either going to die horribly from a) the author deciding it's now pay only or b) popularity bringing a higher percentage of trolls or c) both of the above. --K
It appears to have a single player link. Is that not working / not as good, since both these comments seem to indicate multiplayer only? --CH
I get the impression from Markus that a) won't happen, but b) is a serious risk. There are already griefers. Chris, not sure: I do know that it was single-player to start with, and there will be single-player stuff in future. Markus plans to have [four modes]. --PT
OK. The large "50% of during alpha! Pre-purchase now!" splash in the header is somewhat confusing then. As to the single-player game, it is just as functional (to my knowledge) as the multiplayer, but, to me, building a masterpiece without anyone to comment/criticize/interact with lacks interest. I guess that's a matter of personal taste. --K
Well, you can save your single-player creations and send people links to them, but it's not nearly as fun as building on a multiplayer server. --Anonyman (who was the one to originally recommend this, by the way)
Not sure I'd call it an art form any more than, say, Aquaria or some such. And not sure I'd say it defies categorisation, particularly. But nonetheless, a rather pleasing short little platformer. --AC
Well, I would. It's beautiful, and, unlike almost every other 'game as art' it's also a fun game! Albeit an easy one. The mechanic is pleasing. It's strange the way it punishes you for making progress, but it works very well. Downright eerie. --Vitenka (mildly confounded that it didn't zoom all the way out to real photo-graphics)
I would say that it's definitely art but I'm not sure it's a game. --PT
Whole sites
[Jay Is Games]. A long-running, comprehensive Flash, Java and downloadable games blog. Runs Flash game design contests on a roughly annual basis, all of which have produced some very fun, creative entries.