This is the list I created for a similar thread in 2008 and have updated many times since, although I did better than merely seeing them: I actually met and talked with all of these people.
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I worked at the world’s most popular museum for 12 years and was fortunate enough to meet quite a few famous people in that time, including:
Astronauts/aviators:
Neil Armstrong, Buzz Aldrin, Michael Collins, on the 20th anniversary of the moon landing. (Got their autographs on a book they wrote.)
Alan Shepard (first American in space)
Jim Lovell (Apollo 13 astronaut)
Chuck Yeager (he spoke at NASM every year. He’s a jerk.)
Scott Crossfield (first man to reach Mach 2: very nice guy)
Patty Wagstaff (World Aerobatic Champion)
Hans von Ohain (inventor of the first German jet engine)
Actors/entertainers:
Jack Nicholson
John Denver
Ron Silver
James Doohan
Others:
Walter Cronkite. I gave him an impromptu tour of the Enola Gay exhibit.
Al Gore, before he was nominated for the VP. I gave him a close up tour of the Spirit of St. Louis, which at the time had been taken down for repair work.
Larry King. Gave him a tour of the museum.
Philip Morrison (Manhattan project physicist and author)
Carl Sagan
Kurt Vonnegut
Since leaving the museum in 1996, I’ve had the opportunity to meet a number of other interesting people:
James Cameron
Harrison Ford: I attended a recording session for an IMAX film he narrated. Very nice, unassuming, and shy.
Director Brett Leonard (The Lawnmower Man, Virtuosity)
Producer Frank Marshall (Indiana Jones, Back to the Future, and dozens of other extremely popular films): I interviewed him about an IMAX film he produced.
Writer/Director Steve Oedekerk (Ace Ventura)
Penn and Teller
James Randi (I applied for a job as director of JREF. Didn’t get it.)
Christopher Hitchens (author)
Ralph Nader
Kristen Chenoweth (actress/singer)
Bobby Rahal (IndyCar driver)
Dava Sobel (Author of Galileo’s Daughter and Longitude. I was more excited about meeting her than any famous actor I’ve met or can imagine meeting. Those books rock! When she found out how disappointed I was that I hadn’t brought one of her books to sign, she gave me a copy of the latest paperback edition of Longitude and signed it for me! Complete with the longitude and latitude of her home on Long Island. Very nice lady. )
I’ve also met the directors and producers of virtually every IMAX film ever made, and I’m good friends with many of them.
Met briefly at book signings over the years:
Mario Andretti
Isaac Asimov
Daniel Dennett (philosopher)
Murray Gell-Mann (physicist)
Milton Glaser (graphic artist)
Thor Heyerdahl
Garrison Keillor
Mark Okrand (inventor of Klingon language)
Phil Plait (Bad Astronomer)
Richard Rhodes (The Making of the Atomic Bomb)
In 2006, I spent an evening in Las Vegas having drinks with skeptic Michael Shermer and Mythbusters’ Adam Savage and Kari Byron. The next day I spoke briefly with Jamie Heineman.
In keeping with the spirit of the OP, I’ve been within 20 feet of, but not talked to, Tom Cruise, at a film premiere.