1. Deduce (Grandmaster Edition)
The plain edition of Deduce only costs $0.99, but to get the Grandmaster Edition you need to spend $200. Although it may sound oxymoronic, this game is both simple and complicated, fit for anyone between the ages of 4 and 104. A blend of tic-tac-toe and chess, Deduce does have a big downside: its old-fashioned appearance.
