Well, mine may be kinda lame and tame, but I really like assigning people names, give them nametags and if someone calls them by their REAL name, you take the nametag as a way of keeping score - the one with the most tags wins a prize.
The other is to catch someone crossing their legs - whoever does this the most wins a prize.
Oh, we did this game once where we either had to have our hands behind our backs or tape our thumbs down and we had to open up a pudding pack and whoever ate it first won. And, also who could stick the most q-tips up their nose using their toes.
I know, juvenile, but man! was it funny to watch.