Shamelessly snarfed from filkerdave, this seemed especially poignant in lieu of the passing of Rodney Dangerfield.
Getting to attend the recording session of his "No Respect" album at his club, "Dangerfield's," in New York. He did the album in one take. I didn't recognize him at first as I entered the club -- he was very warm, personable, and just a really nice guy. He paid for a drink for everyone, and the audience was filled with comedy stars (I got in because I knew someone who knew someone). I couldn't wait to buy the album.
Seeing the late Harry Chapin perform live, not once, but twice. The first time I saw him I was 18, attending college for the first time, and just away from my parents. During "Cat's in the Cradle" he first had the whole audience, then the men, then the women sing the chorus. In the last one my voice "kicked in" and it almost sounded like me singing with the rest of the room backing me up. A little later he asked for four volunteers to join him on stage; needless to say, my friends and I all raised our hands. He pointed at me and said, "You, with the good voice, come on up!" That was the first time anybody had ever said I had a good singing voice. The second time I saw him was with his brother, one month before he died.
Getting to go backstage (Radio Hath Its Privileges) at a benefit John Lee Hooker was doing for his daughter, whose house had burnt down. I only saw him from afar, but man, when that guy got on stage, just sitting in his chair and playing, the house rocked.
Getting to see the late Raul Julia on Broadway in "Dracula." Three times (my friend had a crush on him. My friend had good taste...) Drool.... :-)
Getting to see "Sweeney Tood" with the original Broadway cast -- orchestra seats, at a discount!
Getting to see Pete and Peggy Seeger at Foothill College at a benefit. One of the fun parts for me was the "side show" where super_star_girl, in utero, was doing her own "running" (kicking, actually) commentary on the show (poor flower_cat!).
Getting to go to a "Hacker's Conference" with Fuzzball. One of the more poignant moments came after the intros. Todd Rundgren (yes, the singer/musician/producer) introduced himself and paused, waiting for recognition. Only three people in the room applauded; I was one of them. (Richard Stallman, a little later, did the same thing and got a standing ovation.) After the intros, Todd was looking pretty dejected by the fireplace. Fuzzball came over to console him, and he petted her. Another cool moment was Fuzzball playing with a Petster and NHK TV videotaping her.