My vote goes to Pennyless. Though I haven't played it as often as I would like, each time I do it's more fun than the last time. A innovative concept that doesn't involve the well worn Tremors as the focal point.
I vote for Pennyless; because it's one of the more original mini-games this time around. As soon as v3 was posted it was FEATURE NAO! worthy, and of course, the game itself is very fun to play. Nothing like seeing a bunch of people jumping around, falling into a death pit, and fighting to stay inside a bubble shield on a very small floor... oh, and did I mention the explosive needles?
Damn it... Did you have to bring up "FEATURE NAO!" again....