I've met David Bowie. I never talked to him, but apparently I did cry a lot when my mum let him hold me. It was at a restaurant about 20 minutes from my house.
I also got books signed by J.K. Rowling and Ian Rankin.
Oh, and I spoke to Evanna (sorry, can't mind her last name) that plays Luna Lovegood in Harry Potter at a party once. Didn't realise who she was at the time though...