It's been said before, but I'll reiterate that Guns N' Roses does do wonderful covers. My favourite is definitely "Knockin' on Heaven's Door," but their version of "Live and Let Die" and "Sympathy for the Devil" are also awesome.

Also of note, for one of the Nativity in Black albums (I think the second one?) Bruce Dickinson singing "Sabbath Bloody Sabbath" makes me pretty happy, too.