The Mayor of London, good old Ken Livingstone, once bought me a pint of beer at a trade union conference, far more years ago than I care to remember. A very interesting man to chat to.
Also grabbed (not literally!) Paddy Ashdown at the 1992 election campaign on his home territory in Ilminster, Somerset, to quiz him to see if he was gonna do a deal with the tories in the event of an hung parliament, he reassured me that he would not (something he had not clearly stated during the campaign, which is why I asked) and did not notice the T.V cameras around me. That night clips of me and Paddy Pantsdown were shown on the Beeb.
I'm also pretty sure I've served Jennifer Saunders when I worked as a P.O clerk, she was in the local theatre, (which I did not know at the time) and bought some stamps off me, I'm sure I weirded her out a bit because I was looking at her real funny trying to work out who she was, and why she was so familiar, (being a Young Ones & Comic Strip fan) and she was looking at me with one of those "why are you looking at me funny? looks)
Similar experience with Michael Eavis, the guy who runs Glastonbury Fest.
Finally, although it's not me, Joe Strummer used to live not far from me in Somerset and his mate worked in a small village pub. One night Joe was in there with his mate and my drunk brother goes over and says "excuse me mate you're not Joe Strummer from the Clash are you?" Joe replies, "well my names, Joe." That was enough for him, spent the evening chatting to him thinking he was a Joe who happened to look like Joe Strummer!