As a Linux lover, I'm always happy to find games that are a) free and b) cross-platform (that means my non-linux friends can also play with me...
The latest of such games is OpenArena, a 3D First Person Shooter based on the now openly available source code ID Tech 3 (which was Quake 3, lots of COD parts and many more). Aparently the creator of OpenArena took the liverty of also smoothing out some of the bugs of Q3 and the result is an unbelievably rocking experience.
But not enough: the existing mods for Quake 3 (baseq3, OSP, CPMA, ...) are working on it too!
Because it's free it's still very much played online, I saw a lot of servers and will probably try to get my own dedicated server up in a few days...
The address will be posted here.
For all of you looking for a good online shooter, I can very much recommend OpenArena: