When former Chicago White Sox announcer Harry Carey replaced the retiring Jack Brickhouse as the commentator for the Chicago Cubs, he brought with him a tradition-- singing "Take Me Out To the Ballgame" at the seventh inning stretch. When Carey died in 1998, the Cubs continued the tradition, with different people singing the song at each game.
One of my favorite memories of a game was one I attended with my old friend Dan and some other friends. The group Styx, whom Dan considers pretty much to be the worst music group in history, performed it at that game, much to Dan's dread (and our delight).
More recently, mediocre actress Denise Richards performed it-- very poorly. As a singer, Richards, is, well, a mediocre actress.
The most notorious rendition, however, remains Ozzy and Sharon Osbourne's August 19, 2003 travesty: