Given the choice of anyone in the world, whom would you want as a dinner guest?
It's hard for me to narrow it down to one, so I won't insist on that rule. Leaving out people I might genuinely have a chance at, such as famous writers, brings me to:
Stephen Hawking -- because I love quantum physics and would greatly enjoy listening to someone I feel confident is smarter than me.
The Dalai Lama -- again, his existential intelligence outstrips mine. I think I would ask him, "What do you do when you know how to adapt to the culture you land in each life ... but you don't like the one you're in?"
EDIT 5/15/18 -- Today, we're focusing on live people. Someone else reminded me of a historic version that I've penciled in for next week.