42 is Jackie Robinson's number and it is retired
Despite the fact that Jackie's number has been retired by every team in the league, the number 42 is presently sported by one player in baseball. Coincidentally, he plays for the Yanks, and his name is Mariano Rivera.
Well yeah, that's because when MLB implemented the rule in the 90s, it included that any active player with the number would be allowed to finish their career with it.
Mo Vaughn also had it, there are others but off the top of my head I can't remember.