Best one for me was Eric Idle, who I met in a bookstore here in L.A. I have been a die-hard Python fan since I was a kid, so this was better than meeting one of the Beatles for me. Of course I was so nervous I turned into one of the Gumbys when I tried to speak...
Over the years also met/got sigs from: Sylvester Stallone, Roger Moore, Johnny Carson, Ricardo Montalban, Cheech and Chong, Christie Brinkley, Gene Kelly, Gene Hackman, Ray Bolger. Met others I didn't ask for sigs: Jason Alexander, Jeff Garlin, Wayne Knight, Dustin Hoffman, Forest Whitaker, Joe Pantoliano, Raquel Welch, Steve Carrel, Ashton Kutcher. Many character actors I recognized but couldn't name. Basically, you go to restaurants in L.A. a lot and you will encounter your share...
ETA: I did get Idle's autograph and had an artist friend make it into a custom card:
