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.
Nailgun - fires off blue crystal shards of lethal hurting crap
Proximity Mines - if you get close he dies. If you touch he dies. If you don't leave for a minute he dies.
Chaingun - bullet spam wish granted. Ol' Painless is back!