Four Linux Games I Can't Stop Playing - page 3
The Battle for Wesnoth
Who hasn't heard of the Unreal Tournament first-person shooter series? Starting with a late revision of the original game, then carrying on to UT2003 and beyond, the game is playable on GNU/Linux. UT2004 has several game modes that involve a variety of different missions and objectives--not just traditional deathmatch (see Figure 3).
UT2004 stands out among its predecessors and competitors because of its great music, graphics, player control, weapon selection, and online play. I used to love playing UT2004 online, but the prevalence of cheating (aimbots, speed hacks) and the switch to a wireless network connection (which introduces too much latency) has caused my participation to dwindle. Still, in offline "instant action" or single-player tournament mode, it's a heck of a lot of fun.
If you don't want to spend money on the game, you can download a playable demo from the Unreal Tournament site linked above. The demo includes most of the best levels for each game mode and is able to play online.