A serious contender for most difficult game to search for, O is also a contender for the funnest two-player game for iPad 2 and iPad 3. It's the funnest, most chaotic, and most evolved form of air hockey mixed with Hungry Hippos. In the developer's words, "It feels a bit like a two-player variation of Eliss; it's one of the purest non-trivial touchscreen games."

As the game board randomly generates one of three colors, you frantically claim and fling circles either into your own area or your opponent's area until someone reaches a score of 70. The points for each circle increase by 1 (the first piece counts as 0) as long as you collect like-colored circles. The other goal then becomes breaking your opponent's chains. The action all happens so fast. Finger fights will likely ensue both on and off the board, so I've found extra rules are necessary.

A bit of trivia: the name O actually revealed a hiccup in the iTunes store. Brough had to add a "." to get the name long enough for submission. O is on sale for $0.99 for a week as is Glitch Tank.