bjoernvold.com

Nexuiz
Warzone2100
Battle for Wesnoth
Tremulous

And in the addiction department Frozen bubble is the winner.

Of course! Frozen Bubble is like having bubbleshooter.net right on your hard drive!

I'm somewhat addicted to Supertux. Shoot me. lol.

Quake 3 is quite good. never tried quake 4 or quakewars but they are all supported in linux, costs $$ tho