I don't listen to too many cover songs, mostly because they tend to be worse than the originals I've also promised myself never listen to covers of Queen songs anymore, since they're always butchered >.<

As far as a favourite goes it's probably a toss up between Guns 'n Roses - Live and Let die, originally by Paul McCartney i believe or The Clash - I fought the law.

Other good ones i've listened to are Aerosmith - Come Together, Metallica - Turn the Page, Rage Against the Machine - Kick out the jams and Led Zepplin - You shook me.