OpenArena is a community-produced deathmatch FPS based on GPL idTech3 technology. There are many game types supported including Free For All, Capture The Flag, Domination, Overload, Harvester, and more. There are 17 unique player models to choose from and 12 weapons.
Essentially an open source version of Quake 3. It does its job. Not better than the real thing, but definitely a good pick up for any Linux gamer looking for a quick frag.