Already posted so I won't repeat but Placebo's version of Running Up That Hill and Disturbed's version of The Sound of Silence are up there with the best.
I'd also suggest
Nightwish's version of The Phantom Of The Opera
Iron & Wine's cover of Such Great Heights by The Postal Service
Foo Fighters & Brian May covering Have A Cigar by Pink Floyd
Bowling For Soup's version of Summer of '69 by Brian Adams