Jack Bailey - moderator of the bizarre quiz show Queen For a Day from back in the 1950s. He was so thrilled that I actually recognized him! He was on a Caribbean cruise and living in a retirement home in Florida.
Majel Barrett Roddenberry - played Nurse Chapel, Lwaxana Troi, and the computer voice on the Star Trek series. Later married Gene Roddenberry, the creator of Star Trek. I've never met a kinder and sweeter personality. I was last in line at her autograph signing at a Star Trek convention, and she wanted to talk to me forever.
Vanessa Williams - I rode next to her in a shuttle bus between LaGuardia and Newark Airports, and during our conversation, we discovered that we actually have mutual friends!
James Doohan - "Scotty" from the original Star Trek series. I got him to sign a copy of a tape of an episode from the old black & white TV series The Outer Limits from 1962 entitled "The Expanding Human". Turns out this is the very first role he ever played in a Hollywood production. To my knowledge, I am the only person who owns an autographed copy of this tape.
John DeLancie - "Q" from Star Trek - the Next Generation. I played a dirty trick on him at a Star Trek convention in San Francisco. I was standing in line waiting for his autograph. The line went out the door and down the street. Instead of having the fans file past him, he decided to have everyone stand stationary as he walked down the line. When he got to me, he asked "So what do you want autographed?", to which I replied: "Autograph? What autograph? I thought this was the line for the cable car!"
Others I have had fleeting encounters with: Liza Minelli, Linda Gray, Chevy Chase, Patrick Stewart, Michael Dorn, Marina Sirtis, and several others I know I'm forgetting.
The only celebrity I would never want to meet again was Jerry Lewis, who was rude and abusive to a coworker of mine when she approached him to congratulate him for the work he did with handicapped children. Before she could congratulate him, he snapped "Well, I suppose you want my autograph, don't you?"