Portal [The Orange Box] (PS3, Xbox 360, PC, 2007)
OK, so the cake was a lie. But as if Portal wasn't already awesome enough, completion yeilded a superb song sung by GLaDOS - the sinister computer system that... well, play the game and find out. We've stopped the song short here so as not to give away a plot spoiler. But what an awesome and funny offering it is - just listen to the words.
Above: There's no use crying over every mistake - just keep on trying till you run out of cake