My list of celebs I've met is extremely limited, though I've met loads of tennis players- some completely obnoxious like Ann Jones and most of the top women.
Roger Taylor, John Newcombe (

showing my age here) were fabulous while Frew McMillan who commentates on EuroSport is a vile, rude little man who I wouldn't give the time of day to. Andy Roddick is a complete sweetheart as is Kim Clijsters.
Celebwise, Cliff Richard seems to have no time for his fans, never stopping to sign autographs, Terry Wogan was a complete gentleman and a big thumbs up for Phillip Schofield.
(

I'm a bit biased on that one as I've known him since he was ten and while I lost touch when he was living in NZ, we met up again when he was in the broomcupboard on Children's T.V.) He hasn't changed a bit and has both feet firmly on the ground.
I've also met Judi Dench, but that was 30 years ago, and she was lovely. I guess Celebs have their off days like the rest of us.
But according to friends, Babs Windsor and Cilla Black are two of the biggest cows in Showbiz! I cant verify that, I've never met them.