For a long time, the coolest song reinterpretations I heard was Paul Dini singing "Belle" from Disney's Beauty And The Beast in the voice and style of Cruella de Ville from 101 Dalmations. That one exposure changed the entire song for me, moving it from a song about someone longing for a better life to a song about a stuck up, arrogant, pompous bitch.
We have a new contender for the crown.
Neil Gaiman was recently on Minnesota's public radio show Wits and they got Adam Savage from MythBusters on the line. Adam sings "I Will Survive" as Gollem from the Lord Of The Rings movies. Check this out: