What is the funnest most underratted game?

Well it's up to you. Comment bellow with your ideas?
I know that some people find it fun bashing ten winks out of Goombas, shooting the guts out of those space pirates or saving a damsel in distress, but they are vaguely to serious to be called a game that you just play for "fun", in the party sense.
What I mean is out of all of the party style games that you play,
Well mine is Tetris,