As of now I've been playing Halo multiplayer, I find it immense fun. I'm trying to find some other FPS with a great multiplayer element to them. Actual multiplayer, 10 or more other players. What's everyone else playing?

I'm running

AMD Athlon 64 X2 Dual-Core TK-53 1.70 GHz
958 MB RAM
Nvidia GeForce Go 6100
Windows Vista Home Premium