With the soon to be released multiplatform Vulkan API, my interest in switching to Linux for gaming has increased quite a lot, so I'd like to get a good list going of free linux games, preferably with real-time 3D graphics but everything allowed
Examples:
Frets On Fire/FoFix (Guitar Hero clone)
0 A.D. (Age of Empires clone)
SuperTuxKart (Mario Kart clone)
Greedy Car Thieves (GTA2 clone)
Wormux (Worms clone)
Open Arena (Quake3 clone)
Urban Terror (Quake3 mod, free thanks to ioquake3)
Assault Cube
Huge list of open source games on GitHub
Windows games on wine or console games playable through emulation are not Linux games.
You can search for Wine compatible software in their database