We all know Zac Brown Band's latest CD featured the producing work of Dave Grohl, the frontman for Foo Fighters and formerly the drummer for Nirvana.  Last night, Zac returned the favor last night on "Letterman", rocking out to a Sabbath cover.

I guess we all know that Zac loves to rock out.  ZBB's last album was titled The Grohl Sessions, after Mr. Grohl, obviously, and it put Mr. Brown's band at the top of my list of favorite country artists.  Foo Fighters have a new CD out later this year, and I personally think they're the last true rock band left on the planet, so needless to say I really dug this remake of a Black Sabbath classic.