Historical person you'd like in your group? What game?
Another interesting question. I'll go with Robin Williams, whose ability to improvise, play a wide variety of people, general intelligence, and (as far as I can tell) genial personality would make him a great gamer. Doesn't hurt that he's Episcopalian, either.
What game? Something with a little bit of a wacky factor would be fun, but I'd also be interested to see him play something with a more serious bent, because it would be a deviation from the clowny norm.
Anyways, there's my answer.