I know redlemon mentioned this is <a href="http://www.tfproject.org/tfp/showthread.php?s=&postid=1141336#post1141336" target="_new">another thread</a>, but I feel like it deserves a whole thread devoted to him. Plus, there's free downloads. I don't really know much about Dokaka, but I really like the beatbox guitar stuff he's doing. It's insane that someone can actually do the songs this accurately. His "Smells like Teen Spirit" is just so hilarious. It's like you can't stand listening to it after a while, but you can't turn it off.
edit: forgot the link
<a href="http://www.dokaka.com/works.html">Dokaka Music</a>