Voodoo Child, a Hendrix tribute band that were almost as good as the original, they did a lot of gigs in the late 80's, often supporting bands such as the Dammed, Medics and Ian Dury
The Bootleg Beatles, who arguably are better than the originals, as they have been together and playing the songs a lot longer than the Beatles ever did.
The ultimate covers band (rather than single band tribute) however remain the Dark Blues, I've seen them at least once per decade since the 1970's and they are still going strong.