Well, AMV Hell had many-a winner. Can't name a favorite off the top of my head.
So instead, here's this classic:
3. Empty Walls: Elfen Lied (most of the fight scenes and deaths that take place in the anime Elfen Lied put to the music of Serj Tankian's Empty Walls)
Director David O Russel and Crew do the Hustle in a baroque comedic farce with some real humanity to it.