Pretty huge list of free games (found on imgur).
Anchors! (click)
ROLE-PLAYINGPLATFORMERROGUELIKEADVENTURESTRATEGYVEHICLE-BASEDACTIONHORRORSINGLEPLAYER ONLINEMULTIPLAYER ONLINEUNCATEGORIZEDOTHER USEFUL SITESROLE-PLAYING * The Elder Scrolls (Arena/Daggerfall) - The first two Elder Scrolls games.
http://www.elderscrolls.com/arena/ +
http://www.elderscrolls.com/daggerfall/ * Ultima 4 - A classic Fantasy RPG.
http://www.gog.com/game/ultima_4 * Worlds of Ultima: The Savage Empire - A jungle adventure.
http://www.gog.com/game/worlds_of_ultima_the_savage_empire * Ultima World of Adventure 2: Martian Dreams - Steampunk space travel.
http://www.gog.com/game/ultima_worlds_of_adventure_2_martian_dreams * Tales of Maj'Eyal - A beautiful fantasy roguelike emphasizing role-play.
http://te4.org/ * Dink Smallwood - A humourous old PC Zelda-like game. Lots of mods available.
http://www.dinknetwork.com/files/ * UnReal World - Low-fantasy roguelike focusing on historical realism.
http://www.unrealworld.fi/ * System Shock - A classic rebuilt with mouselook. HD mod available!
https://www.systemshock.org/index.php/topic,211.0.html * Magebane 2 - Help 3 monks find an amulet.
http://www.instantkingdom.com/magebane/ * The Spirit Engine (1/2) - Sidescrolling adventures.
http://thespiritengine.com/news.html * Barkley, Shut Up and Jam: Gaiden - A tribute to JRPGs & Space Jam.
http://www.talesofgames.com/related_game/barkley-shut-up-jam-gaiden/ * Elona - A pretty Japanese roguelite. Elona+ is an extensive mod for it.
http://homepage3.nifty.com/rfish/index_e.html * Ahriman's Prophecy - An epic inspired by Final Fantasy VI and Chrono Trigger.
http://www.amaranthia.com/modules/oledrion/product.php?product_id=5 * Summoning Wars - A 3D action game with single and multiplayer modes.
http://sumwars.org/wiki/Main_Page * OFF - A surreal and complex French adventure, translated to English.
http://offgame.wikia.com/wiki/OFF_Wiki PLATFORMER * Cave Story - The definitive indie game.
http://www.cavestory.org/download/cave-story.php * Mari0 - Super Mario Bros. with a portal gun.
http://stabyourself.net/mari0 * Journey to the Center of Hawkthrone - The game from Community. Made by redditors.
http://projecthawkthorne.com/index.html * N - Arcadey ninja action.
http://www.thewayoftheninja.org/n.html * I Wanna be the Guy - Very difficult with free sequels.
http://kayin.moe/iwbtg/downloads.php * Spelunky - Hunt for treasure. Here is an unofficial bug fix version.
http://spelunkyworld.com/original.html * You Have to Win This Game - A metroidvania with a neat visual style. Also on Steam.
http://www.piratehearts.com/blog/games/you-have-to-win-the-game/ * Zineth - Reminiscent of Jet Set Radio. Try and reach the moon.
http://zinethgame.tumblr.com/ * Cybermedic - Similar to Zineth, but with more goals.
http://www.playcybermedic.com/ * Iji - A 2D shooter.
http://www.remar.se/daniel/iji.php * Within a Deep Forest - Atmospheric sidescroller, but short.
http://nifflas.ni2.se/?page=Within+a+Deep+Forest * Knytt/Knytt Stories - Made by the creator of Within a Deep Forest.
http://nifflas.ni2.se/?page=Knytt+Stories * Maldita Castilla - Similar to Ghosts'n'Goblins.
http://www.locomalito.com/maldita_castilla.php * Neverball - Similar to Super Monkey Ball.
http://neverball.org/index.php * Under the Garden - A survival simulator. See the creator's other free games too.
http://www.farmergnome.com/ * Street Fighter X Mega Man - Mega Man fights the street fighters.
http://www.capcom-unity.com/mega_man * In Ruins - An ambient experimental game.
http://www.nullpointer.co.uk/content/in-ruins/ ROGUELIKE * Dungeon Crawl Stone Soup - Very popular example of the genre.
http://crawl.develz.org/wordpress/ * Dwarf Fortress - Complex, strategic, and not a roguelike in the usual sense.
http://www.bay12games.com/dwarves/index.html * Rogue Survivor - Survive a zombie apocalypse.
http://roguesurvivor.blogspot.ca/p/about.html * Angband/Zangband - Angband is based on the lore of Middle Earth. Zangband is newer and based on The Chronicles of Amber.
http://rephial.org/ * NetHack: Falcon's Eye - A 3D overhaul of the classic NetHack.
http://falconseye.sourceforge.net/index.html * Cataclysm: Dark Days Ahead - Survive in an apocalyptic world.
http://en.cataclysmdda.com/ * DoomRL - Based on the game Doom.
http://doom.chaosforge.org/ * Castle of the Winds - 2 part game based on Norse myths.
http://lkbm.ecritters.biz/cotw/download.html * Mercury - Half roguelike, half arcade game.
http://www.decisionproblem.com/mercury/ * Red Rogue - A gory sidescroller.
http://www.redrogue.net/ * Brogue - Controlled by mouse movements.
https://sites.google.com/site/broguegame/ * Grand Rogue Auto - Based on the Grand Theft Auto franchise.
http://grandrogueauto.blogspot.ca/ ADVENTURE * King's Quest (1/2/3) - Classic point-and-clicks.
http://www.agdinteractive.com/games/kq1/download/download.html http://www.agdinteractive.com/games/kq2/download/download.html http://www.agdinteractive.com/games/kq3/download/download.html * Beneath a Steel Sky - Dystopian point-and-click.
http://www.gog.com/game/beneath_a_steel_sky * Transcendence - A top-down space epic Roguelite.
http://transcendence.kronosaur.com/index.html * Treasure Adventure Game - Sail and treasure hunt in 2D. Also available on gog.com.
http://www.robitstudios.com/treasure-adventure-game/ * Broken Sword 2.5 - Uncover a Templar conspiracy in this pretty point-and-click.
http://www.brokensword25.com/spiel/story.htm * The Art of Theft - Stealth-based 2D game.
http://www.escapistmagazine.com/content/games/yahtzee/artoftheft * Naev - Top-down, open world space combat and trading.
http://blog.naev.org/about/ * Zelda Classic - Play the original Legend of Zelda, fan games, and make your own.
http://zeldaclassic.armageddongames.net/what.php * Quest for Glory II - Classic Sierra game remade.
http://www.agdinteractive.com/games/qfg2/downloads/thegame/downloads.html * Flight of the Amazon Queen - Point-and-click inspired by movies from the '40s.
http://www.gog.com/game/flight_of_the_amazon_queen * Dragonsphere - Fantasy point-and-click.
http://www.gog.com/game/dragonsphere * The Wager - A treasure hunting game.
http://www.surprisedman.co.uk/the-wager/ * Heroine's Quest - A newer point-and-click based on the classics.
http://www.crystalshard.net/hq.htm * Gravity Bone - An artsy, noir, blocky game. Highly acclaimed.
http://www.blendogames.com/ * Deity - An isometric stealth game.
http://www.deity-game.com/download.html * The Silver Lining - An unofficial sequel to the King's Quest series.
http://www.postudios.com/company/games/thesilverlining/ STRATEGY * 0 A.D. - An Age of Empires 2 clone.
http://play0ad.com/ * FreeCiv - A Civilization clone.
http://freeciv.wikia.com/wiki/Main_Page * FreeCol - A Colonization clone.
http://www.freecol.org/ * FreeOrion - A Master of Orion clone.
http://www.freeorion.org/index.php/Main_Page * Battle for Wesnoth - Turn-based fantasy like in Fire Emblem, with lots of additional fan material.
http://www.wesnoth.org/ * Open Transport Tycoon Deluxe - A Transport tycoon clone.
http://www.openttd.org/en/ * Unknown Horizons - A city builder similar to ANNO..
http://www.unknown-horizons.org/ * Black Market HD - A space trading game.
http://www.bigblockgames.com/games/blackmarkethd/ * Atomic Tanks - A Scorched Earth clone.
http://atanks.sourceforge.net/index.html * Scorched 3D - Scorched Earth in 3D.
http://www.scorched3d.co.uk/ * Command & Conquer (Tiberian Dawn/Red Alert/Tiberian Sun) - The early C&C games.
http://news.bigdownload.com/2010/02/13/download-command-and-conquer-classic-games-full-free-games/ * A Nation of Wind - A pixelated game similar to Populous.
http://nationofwind.tumblr.com/download * Reprisal - Another homage to Populous, expanding tribes in a small world.
http://www.reprisaluniverse.com/site/playreprisal/ * UFO Alien Invasion - A game similar to X-Com.
http://ufoai.org/wiki/News * 1821: The Struggle for Freedom - Play through the Greek Revolution.
http://www.iceholegames.com/1821game/1821game.htm VEHICLE-BASED * Nitronic Rush - A bright and flashy racer.
http://www.iceholegames.com/1821game/1821game.htm * Rigs of Rods - Driving simulator with soft body physics.
http://www.rigsofrods.com/content/ * Rule the Rail! - Build railroads and then ride them.
http://www.brainbombers.com/train_game_rtr/downloads.html * MTBFreeride - A dirt bike simulator.
http://mtbfreeride.wordpress.com/ * Flightgear - High quality flight simulator.
http://www.flightgear.org/ * Armagetron Advanced - A Tron lightcycle game.
http://armagetronad.org/ * Trackmania Nations Forever - Drive on walls and on other crazy tracks. More content is available by purchase.
http://store.steampowered.com/app/11020/ * VDrift - Concentrates on drifting racing cars.
http://vdrift.net/ * Racer - A car simulator.
http://www.racer.nl/ * Torcs - A regular racing game.
http://torcs.sourceforge.net/index.php?name=Sections&op=viewarticle&artid=3 * Death Rally - Blow up opponents in this classic remade.
http://www.3drealms.com/rally/ * X-Moto - A 2D motocross game.
http://xmoto.tuxfamily.org/ * Rise of Flight - A WWI flight simulator. More content is available by purchase.
http://riseofflight.com/en ACTION * Black Mesa - A remake of the first Half-Life.
http://www.blackmesasource.com/ * Noitu Love - A quick-paced sidescroller.
http://www.konjak.org/index.php?folder=4&file=7 * Hidden and Dangerous - A WWII tactical shooter.
http://www.hidden-and-dangerous.net/deluxe/download.php * The Marathon Trilogy - The precursors to Halo.
http://source.bungie.org/ * Tyrian 2000 - A classic arcade shoot-em-up.
http://www.gog.com/game/tyrian_2000 * Hyper Princess Pitch - Similar to Smash TV.
http://www.remar.se/daniel/pitch.php * Super Smash Land - A Super Smash Bros. demake.
http://www.supersmashland.com/ * Black Shades - Play as a quick-thinking bodyguard. 3D.
http://www.wolfire.com/black-shades * Little Fighter 2 - A beat-em-up that allows four players on one computer.
http://www.lf2.net/ * Super Crate Box - A simple, but fun shoot-em-up.
http://www.supercratebox.com/ * Diaspora: Shattered Armistice - A Battlestar Galatica dogfighter game.
http://www.hard-light.net/forums/index.php?topic=81859.0 * Wing Commander Saga - A fan-made Wing Commander game.
http://wcsaga.com/ * Full Spectrum Warrior - A modern military tactical shooter.
http://www.joystiq.com/game/full-spectrum-warrior/download/full-spectrum-warrior-full-free-game/ * A Fistful of Cows - A western hack-and-slash.
http://www.afistfulofcows.com/ HORROR * Slender: The Eight Pages - The original slenderman game.
http://www.parsecproductions.net/slender/ * SCP - Containment Breach - Survival game based on the SCP mythos.
http://www.scpcbgame.com/ * Ao Oni - A Japanese puzzle/adventure game.
http://mygames888.info/aooni.html * Yume Nikki - Japanese horror. It spawned lots of fan games like .flow.
http://yumenikki.wikia.com/wiki/Yume_Nikki * Ib - Explore a museum as a little girl.
http://vgperson.com/games/ib.htm * Which - The ending changes depending on your choices.
http://gamejolt.com/games/adventure/which/1523/ * Hide - An atmospheric pixelated game.
http://www.superfriendshipclub.com/forum/viewtopic.php?f=12&t=117 * 1916 - Der Unbekannte Krieg - Survive the trenches of WWI with a twist.
http://1916.dadiugames.dk/ * Ascension - A psychological horror sidescroller. Check out the creator’s other games too.
http://www.magnesiumninja.com/ SINGLEPLAYER ONLINE * ATTACK_ON_TITAN - Hack and slash at giants in 3D.
http://fenglee.com/game/aog/ * Super Mario Bros. Crossover - Super Mario Bros. with different classic characters.
http://www.explodingrabbit.com/games/super-mario-bros-crossover * The Republica Times - The precursor to Papers Please.
http://www.dukope.com/ * SuperHOT - A FPS where time only moves when you do.
http://superhotgame.com/play-prototype * Fallen London - A text-based RPG with Lovecraftian elements.
http://fallenlondon.storynexus.com/ * World Golf Tour - A golf simulator.
https://www.wgt.com/ * Card Hunter - A less complex tabletop RPG.
http://www.cardhunter.com/ MULTIPLAYER ONLINE * Team Fortress 2 - A hat collecting FPS.
http://store.steampowered.com/app/440/ * DotA 2/League of Legends - The most popular MOBA games.
http://store.steampowered.com/app/570/ http://na.leagueoflegends.com/ * Spiral Knights - Similar to The Legend of Zelda: Four Swords.
http://store.steampowered.com/app/99900/ * Vindictus - A hack-and-slash dungeon crawler.
http://store.steampowered.com/app/212160/?snr=1_7_7_230_150_1 * Savage XR - A mix between FPS and RTS. Savage 2 is the equivalent MMO.
http://www.savagexr.com/ * Heroes of Newerth - A MOBA in the same universe as the Savage games.
http://www.heroesofnewerth.com/splash/ * Path of Exile - A spiritual successor to Diablo II.
http://store.steampowered.com/app/238960/ * Warframe - A futuristic third person shooter.
http://store.steampowered.com/agecheck/app/230410/ * Quake Live - The everlasting online FPS.
http://www.quakelive.com/#!home * Tecmo Bowl - The old Tecmo Super Bowl with updated rosters.
http://tecmobowl.org/files/ * Neptune's Pride - A space 4x game you can take your time with.
http://np.ironhelmet.com/ * Tagpro - Capture the flag in 2D.
http://tagpro-pi.koalabeast.com/ * Moonbase Alpha - Explore the moon with John Madden.
http://store.steampowered.com/app/39000/ * Hearthstone - A World of Warcraft card game similar to Magic: The Gathering.
http://us.battle.net/hearthstone/en/ * SMITE - The godly alternative to DotA and LoL. Great small community.
https://account.hirezstudios.com/smitegame/default.aspx?ok= * Space Station 13 - Become a member of a space station and keep it running.
http://spacestation13.com/about/ * Myst Online: Uru Live - Explore the worlds of the Myst mythos.
http://mystonline.com/en/ * Planeshift - A truly free fantasy MMORPG.
http://www.planeshift.it/ * Planetside 2 - A sci-fi FPS similar to Battlefield.
http://store.steampowered.com/app/218230/ * Defiance - A MMO that’s also a tv show.
http://www.defiance.com/en/ * Unturned - A 3D zombie survival game.
http://store.steampowered.com/app/304930/ * Happy Wars - A tower defense-like game.
http://store.steampowered.com/app/246280/ * War Thunder - A WWII vehicle combat game.
http://warthunder.com/ * Loadout - An over-the-top shooter.
http://store.steampowered.com/agecheck/app/208090/ * Heroes and Generals - A WWI FPS/RTS.
http://store.steampowered.com/app/227940/ * The Lord of the Rings Online - The Tolkien version of Dungeons & Dragons Online.
http://store.steampowered.com/app/227940/ * Neverwinter - Another Dungeons & Dragons RPG.
http://store.steampowered.com/app/109600/ UNCATEGORIZED * Octodad - A 3D QWOP, in which you control a normal, inconspicuous father.
http://octodadgame.com/games/ * Space Engine - Fly through space in incredible detail.
http://en.spaceengine.org/ * The Powder Toy - A 2D science sandbox.
http://powdertoy.co.uk/ * Passage - A short 2D game about life.
http://hcsoftware.sourceforge.net/passage/ * Starmade - Like Minecraft, but in space.
http://star-made.org/download * Katawa Shuojo - A visual novel made by 4chan. NSFW content can be disabled.
http://www.katawa-shoujo.com/about.php * Hedgewars - A Worms clone.
http://www.hedgewars.org/download.html * Frets on Fire - A Guitar Hero clone.
http://fretsonfire.sourceforge.net/ * Perspective - A platformer and FPS, where you control the perspective of the level.
http://www.seewithperspective.com/ * Toribash - A 3D fighting game in which you create your moves. Also on Steam and has online multiplayer.
http://toribash.com/ * Fish Fillets - A puzzle game.
http://fillets.sourceforge.net/download.php * Broken Dimensions - Walk on walls as a boy in a chicken suit following a ghost.
http://broken-dimensions.dadiugames.dk/BrokenDimensions/BrokenDimensions_Play_Now.html * Digital A Love Story - A computer mystery romance, similar to a visual novel.
http://scoutshonour.com/digital/ * Don't Take it Personally Babe, It Just Ain't Your Story - A visual novel and spiritual successor to Digital A Love Story.
http://scoutshonour.com/donttakeitpersonallybabeitjustaintyourstory/ * Masq - A NSFW visual novel with huge variation of choice.
http://www.alteraction.com/ * Realistic Summer Sports - Play summer sports with QWOP-like reflexes.
http://gamejolt.com/games/sports/realistic-summer-sports-simulator/9769/ * Slave of God - Hang out in a seizure-inducing club.
http://www.increpare.com/2012/12/slave-of-god/ * Peggle Extreme - A mix of pinball and pachinko.
http://store.steampowered.com/app/3483/%29 * Egoboo - A 3D dungeon crawler/hack-and-slash/RPG.
http://egoboo.sourceforge.net/about.html * Façade - An interactive drama.
http://www.interactivestory.net/download/ * OSU - A rhythm game, with lots of Japanese pop.
http://osu.ppy.sh/ OTHER USEFUL SITES * TheFreeBundle.com currently has 12 collections of free indie games. Some overlap with this list exists.
http://www.thefreebundle.com/ * The Spring Engine has led to the creation of some nice RTS games.
http://springrts.com/wiki/Games * Kongregate.com has great flash games.
http://www.kongregate.com/ * MMOHuts.com has a list of virtually every free MMO you could ever want, along with reviews.
http://mmohuts.com/ * PCGamer regularly finds free games to play online or on your desktop. Some overlap with this list may exist.
http://www.pcgamer.com/category/free-pc-games/ * FreePCGamers.com has pages upon pages of free games and their download links. Some overlap with this list probably exists.
http://www.freepcgamers.com/*Software Library: MS DOS (over 2300 free games)
https://archive.org/details/softwarelibrary_msdos_games/v2