On Jan. 18, the British band The Heavy impressed David Letterman so much with their song "How You Like Me Now?" that he did something he's never done before in the history of his program -- he asked for an encore. The YouTube video is the televised broadcast -- which edits out most of the encore -- but you can see it in full in high quality on Letterman's web site. Paul Shaffer and Letterman even perform part of the encore. There have been some great live performances on Letterman, including TV on the Radio's Wolf ... read more