Working in the ATL airport on the main Delta concourse for a couple years, I met all sorts of celebrities. These are my two favorite encounters:
Dave Chappelle came in and bought some movies and shit from us. This was after the show ended. He was a totally down to earth, chill dude that genuinely seemed to enjoy hanging around and talking with us. He hung out for almost half an hour after he bought shit talking about music and random ass bullshit with us. Awesome dude.
My favorite celebrity encounter would have to be boxing promoter Don King, though. I was walking back from the bathroom and saw one of those electric cars going down the concourse... at first I could only see the two bodyguards, because they were so fucking huge they blocked out the view of who was on the back seat. After it passed, though, there was Don King in all his glory, waving a miniature American flag like he was in his own parade and waving at slack jawed passerby.