I've met Dave Trampier, (the guy who did the Wormy comic as well as the famous 'prying the eyes from the gold statue' cover art for D&D)
after he went into seclusion. (He's a really cool guy. I know he's requested to never be contacted regarding the games industry again, so I don't ever talk to him about it.)
I've met David Levy (one of the guys who discovered the comet that hit Jupiter) but only to shake hands.
My really cool one is Robert Bakker. (Bakker is the scientist who discovered the 6-foot tall raptors (actually called Utahraptors) featured in the Jurassic Park films. He is also the basis for the character of Alan Grant, as he was written in the original novel.) My father and I were going to see him speak, and he pulled me out of the crowd, shared his dinner with me, autographed a copy of his book, and drew me a poster of a little-known dinosaur species. (There is a part of his whole act when doing speeches where he proclaims that children are infinitely smarter than adults, and draws a detailed anatomic drawing of a dinosaur. Inevitably, every adult in the audience will fail to identify the species, at which point he will call on a "random" child, who of course knows the answer, having been coached beforehand.

) It was a really cool experience.
I met a woman at a con that I had never heard of who was introduced by the organizers as a 'writer for White Wolf.' Can't remember her name. I do recall that she was one of the worst people I've ever met.