More of a personal memory than a top baseball moment, but Biggio's leadoff homer in Game 7 of the '04 NLCS was pretty neat for me. I was stuck playing a concert that night, and when my particular ensemble wasn't playing we had to sit in the audience with everyone else. So a friend of mine brought a 4" portable TV and we all huddled around it in the very back. There were about ten of us all crowded around his seat watching the beginning of the game, and when Biggio took that ball out, we were probably louder than whoever happened to playing on stage.
Believe me, no one cared. We were a shitty, shitty band and nobody wanted to be there. All of us performing, our band director, and the audience (bless their hearts for showing up) just wanted to wrap things up as quickly as possible and get home before the game ended.