Beatallica rulz!

I'm not sure who they are exactly, as they prefer to remain anonymous, but Beatallica perform Beatles songs in the style of Metallica, which you might have guessed from their name. They pull it off really well; the singer does an uncanny James Hetfield impersonation (you know, like, "I wanna hold your hay-yay-yand!"), each song is given a mash-up-like title combining the names of songs from the two bands, and the lyrics are hilariously altered in places to better reflect a meatheaded metal mentality.

Best of all, all their tracks are made available for download, completely free of charge, at their website, beatallica.com. Check it out.