Panic Room - Bitches Crystal (ELP)
Completely rebuilds the song from the ground up with a totally different arrangement.
Turisas - Rasputin (Boney M)
The arrangement is actually very close to the original, just with louder guitars and drums, and a different vocal style. Many disco standards just *work* as metal songs.
Gimme Gimme Gimme - Yngwie Malmsteen (ABBA)
It's also better than any of Yngwie's own songs, and proves Bjorn and Benny are far, far better songwriters than he is.