Halfbrick's entire library is on sale right now. The whole darn thing. Every game can be had as a free download right now, from Age of Zombies [$0.99] to Monster Dash [$0.99], an a-to-z reference that would work better if they had any games that had letters later in the alphabet. No word if this is a temporary sale, or like what NimbleBit did after they hit it big, just making everything free to download because forget paid games.
Here's a list of the paid games gone free.