Fans of George R.R. Martin's epic tomes know that "The Rains of Castamere" is an infamous tune in the story-- it describes a brutal victory by noted villain Tywin Lannister, it appears numerous times and is discussed by major characters, and plays a part in a pretty pivotal (and emotional) point in the third book. Nerd notes aside, for all the chatter about the song it's never been heard until now-- George teamed up with The National to bring it to life for the HBO series.

It's been debated, but I'm comfortable saying that this is pretty much perfect.