Games I play from time to time. Of course all of them are linux based.
Crack-attack
Very nice OpenGL tetris like game. Can be found in ubuntu repositories. Check the site. Be warned however that this game can be very, very addictive.
apt-get install crack-attack
World of Padman
A game I heard recently about but captivated me right away. Based on Quake engine but the levels and weapons are all the fun. Check their site. The install is based on an executable script which can be downloaded from their site.