TeamFortress 2Since a while steam has been ported to linux as most of you know.
TF2 is free to play on steam , good old times.
Runs pretty good , bit unstable but the performance is screaming.
Its been reported that valve got higher frames per second than on windows
http://www.teamfortress.com/index.phpSavage2Another game Id like to recommend is Savage2
Its one of those rare games that is actually really good.
Most people will probably not play it when they see the screenshots and think "not my kinda game"
Thats what I thought at first, the unique mixture of FPS/melee and a commander that plays a strategy game is brilliant.
And its fast, really fucking fast, adrenaline like.
This one is also completely free and runs on linux/windows/mac.
http://www.savage2.com/en/main.php