Who's the most interesting person you've met?

I generally don’t rate people, but I had a terrific conversation with Bob Costas after he gave a speech at my school (this was over 35 years ago) about his love of baseball, changes in sports (both rule changes and changes to the surfaces played on), dealing with players and agents and the fact that he (like myself) used to memorize the statistics on the back of baseball cards (the difference being that he found a way to make money from it by majoring in Communications at Syracuse).
The whole afternoon (both the speech and the talk afterward) was enlightening.