This weekend I was introduced to the fabulously complicated and more than a little geeky (but fun) game, Cosmic Encounter. The rules are really way too long to summarize here (and honestly, we played it for about four hours and I think I was vaguely getting the idea of how to play it somewhere in the last half an hour or so). The best part of the game, however, is that you are assigned an alien identity that gives you special powers that the other players don't have. There are dozens of alien-types in the version of the game that we were playing, each of which comes with a hefty paragraph or two describing its particular gift (caution: after several drinks these hefty paragraphs with ambiguous instructions may be difficult to accurately interpret). This makes each game rather complicated at the beginning (since you are trying to figure out what you can to do the other players and what they can do to you) and would also (I imagine) keep the game fresh and interesting even after playing it a million times. My favorite part about the alien powers, however, was taking alien portraits of all the game players.
I am not a full-fledged Cosmic Encounter convert yet, but I would love to play it again just to try out the powers of a different alien.