I can only lay claim to a bunch of "bumps and near-misses" - 

• I met Mark Collie (country singer) when he came to our radio station in the early 90s.  I was producing a talk show in those days... so I got to talk to a few "names" on the phone - Gordon Liddy, and Mike Farrell (BJ on M*A*S*H) were a couple I can remember from those days. 
• A few years before that, Bob Hope came through our community to do a show, and all of we newsies went out to the airport for a q&a session.  I managed to get into the front row of reporters, and spent about 20 minutes 3' away from the man.  Incredible, at almost 90 years of age, he was hard of hearing but mentally still very sharp.
• And, my personal favorite - getting to ride along with the US Army's Golden Knights parachute team when they went up to jump. They double-strapped me in by the jump door so I could lean out (at altitude) to take pictures of their jump. What a great bunch of guys.

The best stories I personally know are from my dad.  He played French Horn in the USAF's 505th band in the late 1940s and early 1950s, and some other pro work later.  He then taught composition for many years.  Over the decades, his work brought him in contact with the likes of Dizzy Gillespie, Buddy Rich, and a number of other major players of the big band and "primal jazz" eras. 

He had his adventures, too - he was at a convention in Philadelphia sometime in the 1980s and heard that there was a gala being thrown for Eugene Ormandy's 80th or 90th birthday.  He put on a tux and went to the hotel where the party was.  He went up the stairs to the floor of the event, got in line, shook hands with the maestro, and managed to get out before security nabbed him.  These days, it would be hard to get away with something like that.

Fun thread, folks.  I'm enjoying it.

Pissed in the urinal next to Rick Derringer at the Great American Guitar Show - Philadelphia