Man, there's too many good covers for me to really go through. My favourite sort of cover is the way covers are used by the better industrial artists, totally skewing the song to give it new meaning, either by changing the lyrics, adding samples, or simple vastly altering the style of delivery. Prime examples might be Coil taking Tainted Love and, with a funerary pace, soul-piercing synth stabs and an incredible video turning it into a song about the tragedy of AIDS, and pretty much everything Laibach have ever touched, for example, their version of War, where after the line 'War! What is it good for...' a choir starts singing the names of big American corporations over bitching industrial beats.