"I Got A Feeling" Psycho Version (with a bit of Freebird thrown in at the end)
Beyonce's "Halo" Metal Version
Slipknot's (who gives a crap what it is) Radio Disney Version, complete with angry fan comments
Bee Gees "How Deep Is Your Love" Death Metal Version
Metallica's "Enter Sandman" Smooth Jazz Version
Seriously, the Metallica one almost sounds like something Richard Cheese would do.
Billy the Poet I seem to recall a number of bands whose whole careers were basically this.