here's a small list:
Left 4 Dead
COD 4, 5, (whatever is latest/greatest), World At War
Team Fortress 2
CS:S
Saw a few older games being played too, such as battlefield 1942/ BF2, diablo 2, warcraft 3, quake 3, and such. Ya never know what games might pop up.
As far as consol games go the guys that run the LAN are always ontop of the greatest/best available.