Dance Dance Revolution
If you ever doubted the creative potential of Minecraft, there's something you need to watch. User longhornman99001 has successfully recreated a working version of Dance Dance Revolution in single player.
This in-game version of DDR works just how it does in real life. The game is started with a "coin-slot" into which the player places a Minecart as capitol. A steam of colored wool comes down the track in front of the player, they then step on the corresponding pressure plate causing the stream to end. User Longhorn even included a music box soundtrack and working scoreboard.
It's doubtful he'll be giving out the recipe anytime soon, but plans are the in the works to put this on a server.