- Black Mesa - Remake of the first Half Life game.
- Warsow - Fast paced multiplayer FPS.
- Quake Live
- OpenArena - Quake III Arena clone.
- Mech Warrior 4
- Ace of Spades - Multiplayer Minecraft inspired game with guns.
- Grand Theft Auto 1
- Grand Theft Auto 2
- Soldat - 2D Counter Strike with jetpacks.
- Marathon Trilogy - Bungie made this game series before Halo. It's considered to be the spiritual predecessor of Halo.
- Alien Swarm - Top down multiplayer shooter made by Valve.
- F.E.A.R. Combat - Online multiplayer FPS.
- Hidden & Dangerous
- Wild Metal - Action/strategy game made by Rockstar.
- Xonotic - Fast paced multiplayer FPS.
- Red Eclipse - Fast paced multiplayer FPS.
- Wolfenstein: Enemy Territory
- America's Army
- Noitu Love - Great action filled adventure game made by Konjak.
- Assault Cube - Fast paced multiplayer FPS.
- N
- Super Crate Box is a fast paced and addictive arcade game.
- Probability 0 - Platformer with roguelike elements.
- Tyrian 2000 - Classic Shoot 'em Up. There's also an open source project of the game here: http://code.google.com/p/opentyrian/
- Stealth Bastard - Stealth based platformer.
- Hyper Princess Pitch - Smash TV clone.
- Hydorah - R-Type/Gradius clone.
- Virax
- Verminest - Arcade shoot em up.
- Hurrican - Remake of the old Amiga classic.
- Super Smash Land - Super Smash Brothers demake.
- Shoot First - The Binding of Isaac meets Smash TV.
- Open Liero X - Real time Worms clone.
- Frozen Bubble
- Little Fighter 2 - Great beat 'em up with both single player, co-op and battle mode.
- Dwarf Fortress
- Command & Conquer - The first C&C game.
- Command & Conquer: Red Alert
- Command & Conquer: Tiberian Sun + Firestorm Expansion
- Open Transport Tycoon Deluxe
- Hedge Wars - Worms clone.
- FreeCiv - Civilization clone.
- FreeCol - Colonization clone.
- 0 A.D. - Age of Empires 2 clone.
- OpenRA - Red Alert Open Source Project.
- The Battle of Wesnoth
- Scorched 3D - Scorched Earth clone.
- Atomic Tanks - Scorched Earth clone.
- FreeOrion - Master of Orion clone.
- Ufo Alien Invasion
- Warzone 2100
- A Nation of Wind
- The Wager
- S.W.I.N.E.
- Advance Strategic Command
- Black Market HD
- Transcendence - Transendence is a real time space exploration game with some roguelike elements.
- [King Arthur's Gold (http://kag2d.com/en/download) - Aka. KAG. Takes the building aspect from Dwarf Fortress, the strategy from Age of Empires and the class system from TF2 and mixes it with online multiplayer mayhem.
- Dungeon Crawl Stone Soup
- Brogue
- ToME
- ADOM
- NetHack
- Angband
- DoomRL
- Cataclysm
- Rogue Survivor
- Desktop Dungeons
- POWDER
- The Slimy Lichmummy
- Mercury
- IVAN
- Castle of the Winds
- System Shock 1 - The old classic. Works on newer systems and has mouse look.
- The Elder Scrolls: Arena - The first game in the Elder Scrolls series.
- The Elder Scrolls: Daggerfall
- Dink Smallwood - Old PC adventure/rpg with a lot of extra fan made stories.
- Magebane 2
- Arkoss
- The Spirit Engine
- The Spirit Engine 2
- Ultima 4
- Ultima: Savage Empire
- Ultima: Worlds of Adventure
- Delver - First person dungeon crawler with roguelike elements.
- Beneath a Steel Sky
- Octodad
- King's Quest 1
- King's Quest 2
- King's Quest 3
- Quest for Glory 2
- Flight of the Amazon Queen - You've got to emulate it through ScummVM.
- Dreamweb - You've got to emulate it through ScummVM.
- Broken Sword 2.5
- A Tale of Two Kingdoms
- Trackmania Nations Forever - One of the best free racing games out there.
- Death Rally - Old classic. Weaponized cars on the race track. Cheat, kill and annihilate your way to victory.
- Nitronic Rush
- VDrift
- TORCS
- Racer
- Team Fortress 2
- Tribes: Ascend
- Super MNC
- Gotham City Impostors
- Battlefield Heroes
- Age of Empires Online
- Dungeons & Dragons Online
- Lord of the Rings Online
- Everquest 2
- DC Universe Online
- World of Tanks
- Realm of the Mad God - MMO with permadeath.
- Bloodline Champions
- League of Legends
- Heroes of Newerth
- Spiral Knights
- Savage 2
- Ao Oni - Horror Exploration.
- Yume Nikki - Horror Exploration.
- .flow - Horror Exploration.
- Ib - Horror Exploration.
- SCP Containment Breach - Horror/survival game based upon the SCP Foundation stories.
- Slender - Based upon the Something Awful creepy pasta.
- Katawa Shoujo - Visual Novel (NSFW). Supports Windows Mac and Linux. Cached mirror to download page: http://webcache.googleusercontent.com/search?q=cache:7FoQ8A8MeVEJ:katawa-shoujo.com/download.php+&cd=1&hl=en&ct=clnk&gl=no&client=firefox-a
- Digital A love Story
- Don't take it personally, babe, it just ain't your story - Visual Novel. Spiritual successor of Digital A Love story.
- Frets on Fire - Guitar Hero clone.
- FlightGear - Flight Simulator
- Moonbase Alpha - Aeiou!
- Under the Garden - A sequel named Under the Ocean is in development.
- Which - Short horror game.
- Spring Engine - Many different games made for the Spring Engine.
- Gravity Bone
- Osu! - Osu closely resembles Elite Beat Agents and other rythm games. Highly customizable and many different songs.
- StepMania - StepMania is a dance and rhythm game. Highly customizable and many different songs.
- La Mulana
- Cave Story
- Iji
- Spelunky is a roguelike inspired platformer made by Derek Yu. The Xbox remake heavily expands upon the original game in every single way. The PC version has also a lot of different mods which you can download. If you're going to download the original PC version, then I highly recommend you download the unofficial 1.3 version of the game. It fixes a lot of bugs and it also runs much smoother.
- Eternal Daughter is a metroidvania released by Derek Yu.
- Treasure Adventure Game. You can even add the game to your GOG-catalogue.
- Hero is the first game in the "Hero" series. It's only in black and white and it's inspired by old games from the Commodore 64 and Atari era.
- Hero Core is a minimalistic metroidvania. This is the second game in the "Hero" series and it's a full fledged metroidvania (compared to the first game). It's available on both PC and Mac.
- Hydra Castle Labyrinth is a Japanese metroidvania developed by E. Hashimoto (aka. Buster). Here are some mirrors if the original link doesn't work: http://jayisgames.com/archives/2012/01/hydra_castle_labyrinth.php http://vsrecommendedgames.wikia.com/wiki/Hydra_Castle_Labyrinth
- Lyle in Cube Sector
- An Untitled Story
- Within a Deep Forrest
- Knytt
- Knytt Stories
- Poacher is a game created by Yahtzee Croshaw. Yes, that Yahtzee.
- Frogatto & Friends
- L'Abbaye des Morts ZX-Spectrum graphics with Manic Miner/Jet Set Willy gameplay.
- You Have to Win This Game - Retro exploration platformer.
- I Wanna be the Guy
- I Wanna be the Guy Gaiden: Act 1
- suteF
- Arvoesine - Short and hard platfomer which closely resembles Ghosts'n Goblins.
- Phenomenon 32 - Phenomenon 32 is a really hard exploration based platformer. It somewhat resembles Zelda 2.