Mozart

Wolfgang Amadeus Mozart is a character who might appear in a future battle. He was refernced in Epic Rap Battles Of History 27 by Santa Claus, in his Naughty List, along with 3 other characters who already appeared in rap battles (Master Chief, Mr. Rogers and Moses)

Possibilities

 * Skrillex (mentioned by Nice Peter)
 * Ray Charles
 * Beethoven (unlikely, but could appear as a 3rd party rapper)
 * Some other pop singer (not Justin Bieber)