Another variation on the music/ballet link (apologies if we've played this game before). Can you think of a piece of music that should by all rights be a great ballet, yet for whatever reason doesn't have a great dance sutured to it (unlike, say, B+T's Serenade)? The first piece of music that comes to mind for me is Prokofiev's Classical Symphony. Many have choreographed it, no doubt, but there's no definitive balletic interpretation, at least not to my sensibilities, and I'm not sure why--it's tuneful, not terribly long, full of dance rhythms, etc.
Any others come to mind?