Met a few folks at historic races and the like and ignoring all business/political figures, three stick out;
1) Bob Hoover at the Reno Air Races, very, very brief in a reception tent where he spoke. Google Bob Hoover... I was honored to even be near him. My one impression; humble.
2) Gordon Lightfoot at the New Haven Airport. Early 90's. Ironically, I had tickets to see him earlier in the Summer at a concert that was cancelled due to his illness. Later that Summer, I flew my girlfriend (now Wife) and I to New Haven to see some friends. As we were leaving, an older Canadian registered jet pulled next to our tired looking Piper Cherokee. The Hawker had hush kits and I took a few steps over to look. Gordon and his band exited the airplane, saw me looking and made small talk. One said "Like the cookie cutters?" (slang for hush kits). "Pop in" another said. I mentioned that I had tickets for a cancelled show and they offered seats at that night's show, but I had to be back. Stupid decision, looking back I should have gone. I looked in the plane, the crew was cleaning it and there were bags full of cans and bottles; spring water, orange juice, etc....I guess that is how you keep doing it through your 60's...
3) Sir Roger Moore, Piccadilly Street, London, late 1998. I was on our honeymoon and my Wife caught an awful cold. Late one night I took a walk to get her some cold medicine. I was walking on Piccadilly when I saw two couples in formal wear approaching, actually his distinctive voice caught my attention. The man had a presence that can't really be described. He noticed my "wow, its James Bond" stare, and the conversation as we passed was IIRC:
Mr. Moore; "Yes, I am who you think I am..."
Me; "Uhhh...good evening Mr. Moore"
Mr. Moore: "Ahhh, a Yank, what brings you to London?"
Me: "I'm on my honeymoon"
Mr. Moore: "Honeymoon........and you don't have something else to be doing beside walking in the rain??? GO man!"
Then they walked off laughing...