Note: Some of these require a DOS emulation program, such as DOSbox.
Download DOSbox here: http://www.dosbox.com/


Spelunky - A procedurally generated platformer made with GameMaker
http://forums.tigsource.com/index.php?topic=4017.0

Dwarf Fortress - "A single-player fantasy game" with a procedurally generated world. ASCII graphics.
http://www.bay12games.com/dwarves/index.html

Warsow - A fast paced cell shaded FPS. Comes with x86, x86 portable, and x64 executables.
http://www.warsow.net/

Gang Garrison - A 2D sidescroller "demake" of Team Fortress 2
http://www.ganggarrison.com/

Wolfenstein 3D - The game that started the FPS genre. Requires DOS emulation.
http://www.dosgames.com/dl.php?filename=ft...are/1wolf14.zip

Doom - One of the first truly great FPS games, spawned a crapton of clones. Requires DOS emulation.
http://www.dosgames.com/dl.php?filename=ft...oom/doom19s.zip

Duke Nukem 3D - The prequel to Duke Nukem Forever, a game that's probably not going to be released for a while. Requires DOS emulation.
http://www.dosgames.com/dl.php?filename=ft...re/3dduke13.zip

Duke Nukem 3D high Resolution Pack - DN3D with better graphics, also no need for DOS emulation.
http://hrp.duke4.net/

Elder Scrolls II - Daggerfall - Largest Elder Scrolls game ever, with over 15,000 square miles to explore. Requires DOS emulation.
http://www.elderscrolls.com/downloads/down...-daggerfall.php

Toribash - Innovative fighting game, where there are no predefined moves. You control everything the player character does.
http://toribash.com/

Facewound - A personal favorite, Facewound is a zombie apocalypse themed 2D sidescroller shoot 'em up. It's got 3D accelerated physics, tons of weapons, and plenty of enemies.
http://facewound.com/


If you can think of any others, post them.

been wanting something like this. All for pc? I still have a box I can use.

Yeah, they're all PC.

Battlefield Heroes - 3rd person shooter, and probably the best free game I have ever played.
http://www.battlefieldheroes.com/

FlyFF - A decent free MMORPG, however to truly be good at the game you'll have to spend a little money.
http://flyff.gpotato.com/?m=welcome

Phantasy Star Online : BB - Probably the best Online RPG I have ever played. I'm a total Sega fanboy so you probably won't have the same experience I did.
http://www.schtserv.com/

Quake Live- A realy cool, in browser multiplayer FPS. If you're into the classic Quake games, or FPS, try it out. It's really good, considering it's a free in browser game.

http://www.quakelive.com/

Not a game in particular, but http://hotud.org/home is where I've downloaded many an abandonware game.

Update on this one, now works on Linux.