Games I end up playing when Me and my brother have a few friends over for lan or played in the past:
Generals/Zero Hour
BF1942/desert combat
Rome total war
UT 2004
Would be playing more games but we haven't had a lan for a while despite my brother purchasing a few more Northwood and prescott based setups, as his friend's are still stuck with P3 setups, and before he got them we still had P3 933mhz based setups as guest computers that were usually used by his friends should they not bring a computer or for other reasons.
That's about it really, my brother is anti-cs or generally doesn't like playing a lot of FPS games besides battlefield. If I go to a friend's lan though we usually will end up playing zero hour, cs (1.6 or source), BF (Desert combat, Vietnam, BF2), COD2 and occasionally I'll convince them to play esf or ns.