I've met Mike Doughty and Adam Richman. Mike Doughty was in stunned silence because of my chatty autistic brother being there, and Adam Richman was very personable. Dunno if this counts, but my late great-uncle (I think that's how he's related to me) was Marion Tinsley, who was considered the world's greatest checkers player. Never met him, though.
EDIT: Since people are putting down who their family members have met, I may as well do it too, just for fun. My mom's met Diane Kruger (from the National Treasure movies) and Joshua Jackson (from Dawson's Creek) at the wedding of two of her gay friends, and she worked with the wife of Jack Emmert, the creator of City of Heroes. My mom told her that I wanted to play the game, and so Jack sent me a year's worth of free game time and a t-shirt. My dad got a marshmallow smeared with paint from one of the members of the Blue Man Group when he went to Vegas. And then my step-grandfather went to college with Halle Berry's mother, and apparently held Halle's hand when she was three. He also claims to have met Charlie Chaplin and various others.