An a capella version of the Turret opera at the end of Portal 2? Sure:
That’s the Turret opera, which you know if you completed the game and saw this (you might not want to play this video if you haven’t gotten there in the game yet):
It’s not, of course, Jonathan Coulton’s ending theme. And there are some sound effects, so it’s not 100% a capella (NOTE: Or maybe it is. See comments below). But it’s pretty impressive. You can buy this version on iTunes here, or just play the video over and over, or play the game and get to the end.
Sebastian Wolff, who arranged the a capella version, and Acquire A Capella, the performers, are from UC Santa Cruz. The Acquire crew did a previous video for an a capella version of The Lonely Island’s “I’m On a Boat” that went viral a couple of years ago, so they know how to get attention. Mission accomplished.