ok tf2, css, and 1942/dc final are all good...though the best mod ever for bf1942 was pirates, especially when everyone starts talking in bad cpt. Balbosa accents.
Interestingly enough TFC was the game that got me into lanning back in 2000, and that LAN party introduced me to counterstrike and got me interested when my team won the tourney (had 6 teams 10 per team)....kinda wild that here 8 years later instead of TFC there's TF2 and instead of CS there is CSS. That is the mark of very well designed games when they can hang that long.