This is indeed a cool thread, here's my contribution:
1) Chris Cormier: laid back as hell.
2) Nasser: Great guy, took a picture with him and he took the
time to talk and socialize...
3) Tom Prince, Frank Sepe, Milos Sarcev, the Met-Rx guys ...
Prince is the man, and Sepe was okay.
4) Eddie Robinson: he is an old favorite of mine and he was
a funny funny guy when I met him.
5) Vince Taylor: caught him while he was rushing off somewhere,
but he was cordial enough to get a quick photo with me, I
thought that was pretty cool.
There are more, but I can't remember them right now. There
weren't too many bad experiences with pros, they are generally
decent folk who'll be cool if you avoid the "what do you do for
biceps?" questions...