The most downloaded iPhone app. is currently Bubble Ball.
The most downloaded iPhone app Bubble ball was designed by Robert Nay in 2010. In early 2011, downloads exceeded 2 million in only a few weeks. The game is a physics-based puzzle game with simple graphics.
Prior to that, the most downloaded iPhone app. used to be Angry Birds, a game designed by the Finnish game-making company Rovio; a game where one can catapult feathered missiles into a variety of structures that shelter the green pigs who have stolen ones eggs.