CS is just a poor excuse of an online game, because althought i'm constantly told that it is a tactical game ... everytime i've played i've thought Q3:A has more bloody tactics.
Day of Defeat is a far better mod as far as i'm conserned, still alot of mindless tactics ... however they've actually coded in thier own Anti-Cheat measures, so althought everyone bitchs that people have aimbot and crap - really its all down to ping in that game.
Bid for Power is outstanding - sadly is extremely demanding on any system its played upon, and even more unfortunatly its got the Quake3 Native NetCode ... which means online play for anyone using a connection under 256 Broadband will just seem like they're playing Doom on a 386sx (not fun)
Had some amazing home lan matches though, when ya hook all 8 machines up here - ki balls all over the place, homing discs comming for you so ya runn behind someone else and make it follow them - hehee alot of fun
Earths Special Forces is graphically nice, and DragonMod Z is playably nice

... unfortunatly Half-Life Modders require you to actually be competant net coders so its even worse for slower connections.
There that new one Natural Selection - pretty cool, kinda like if C&C and Renegade were thrown in together netwise, and given an AvP twist

Certainly fun.
Anata aru kowagaru no watashi! 