My favorite new YouTube discovery of the week is the "Epic Rap Battles Of History" series.  You post comments/ideas on who you want to see do battle, and these guys make it happen.  Check out Einstein and Hawking's throwdown after the jump - plus Sarah Palin vs. Gaga, Justin Bieber vs. Beethoven, Abe Lincoln vs. Chuck Norris, and much more.  (Note: Many of these are NSFW.)

Justin Bieber vs. Beethoven:

Abe Lincoln vs. Chuck Norris:

Hulk Hogan vs. Kim Jong Il:

Sarah Palin vs. Lady Gaga:

If you could pick the next one, who would it be?