I remember Mariano Rivera once saying that before he retired, he wanted to play centerfield in a game and start a game one last time. His injury fielding fungos in the outfield killed the centerfield fantasy, and I'm not sure why the Yankees didn't give him one last start, for old-times sake.
That said, you see a lot of players who fulfill their diamond fantasies. Pudge played 2B, Don Mattingly (a left-handed thrower) played 3B (Rizzo played 3B out of necessity). And then you have your Shane Halter and Andrew Romine types who get to play all nine positions in a game. And Jake Rogers pitching an inning. This is the kind of stuff that makes baseball fun, even if it just done because the situation demands it. Heck, Bill Veeck hired a very, very tiny (3 feet 7 inches) Eddie Gaedel to pinch hit in a game against the Tigers. How about Adam Greenberg facing R.A. DIckey in his first MLB at bat in 7-years after Dickey hit him in the face with a 92 mph fastball. Publicity stunts (for lack of a better term) make baseball great.
Here's my wish: I'd like to see Miguel Cabrera, who I watched play shortstop in the minor leagues (I think he played the position over 167 games) play the position for one inning during a throwaway game.