Clone Hero - Clone Hero is a free rhythm game, which can be played with any 5 or 6 button guitar controller...
Hexen II - The Hammer of Thyrion project is a cross-platform source port effort of Raven Software's Hexen.
Osu - Osu is Music, Rhythm, Single and Multiplayer video game developed by Dean Herbert.
Black Mesa - Black Mesa is a third-party remake of Half-Life developed and published by Crowbar Collective.
StepMania - Rhythm game for Windows, Mac, and Linux.
Quake - Quake is a series of first-person shooter video games released by id Software.