Just a brief note right now: I’ve had a quick run at AssaultCube, and found it worthy.
I like that the original Cube/Sauerbraten game has gotten a makeover and gotten a little more … focused. It retains its speed and playability, and adopts a much more … focused … theme.
Give it a try. 🙂
Motho ke motho ka botho 
I threw up while playing it… 😦
i like it too
Have you tried Xonotic (a fork of Nexuiz)? It’s another excellent FPS for Linux. Pretty good graphics. Very fun.
I wonder if there is a command line FPS. 🙄
Probably not exactly what you were thinking, but it works 🙂