Sigur Ros & Game of Thrones, Sitting In a Tree
They covered "The Rains of Castamere" and and and
...and they make a cameo appearance in the upcoming season! They form a human pyramid and Tyrion climbs on top to deliver an epic speech about three-eyed ravens or something. I just made that up, but still - you know it's going to be awesome, whatever it is. Jonsi kinda sounds like a baby White Walker anyway, so it's a natural fit! Check out a clip of their version of "The Rains of Castamere" here. The National recorded a version as well, it's here (and it's awesome).