Quite a few. Warcraft 3, UT2k3, Starcraft, AVP2. Can't really think of a lot of the rest at the moment. We've never had a problem with it.
I don't play online..but it's through another card, which is usually disabled when we're playing on the LAN.
It bothers me because it's not lag..the screen dosen't jerk, or freeze, or anything.