There are quiet a few good covers out there.
Some musicians just have a knack for covering songs really well, Dave Grohl is one of those.
He's done a lot of covers but there are two in particular that he did which I absolutely love.
Paul McCartney's Band on The Run covered by the Foo Fighters.
Prince's Darling Nikki covered by the Foo Fighters.
Elton John's Rocket man covered by Puscifer (<---my personal favorite)
Unfortunately I can't post links yet
