One of my favorite songs ever is the Flight of the Bumblebee by Nikolai Rimsky-Korsakov. I thought: wow, that's fast and difficult and amazing and very bee-ish.
Well, this guy called György Cziffra wrote his own arrangement . . . which is about ten times harder. Below, he's playing it. The quality's not perfect, I'm afraid -- the recording is about fifty years old. Alternatively, to see someone's fingers, see:
http://www.youtube.com/watch?v=ZKCZZf6ixj4&feature=related (that's not the person who wrote it, though, which is why I like the below)
Click to view