Chris Buffa (Modojo): With more smartphone and tablet games going free-to-play, it's interesting to see the lengths publishers go towards implementing in-app purchases. Few do it well, while most seem greedy. Gameloft sits in the middle, and its newest iOS and Android title, Iron Man 3, is a prime example why. This action-packed endless flying game includes the sorts of features that hardcore fans crave, from 18 different suits of armor (including the Iron Patriot and War Machine) to famous villains like Crimson Dynamo and M.O.D.O.K. You could in theory enjoy the game for hours without spending a dime, and it's certainly fun despite some issues. Build the aforementioned armor, though, and you'll soon realize everything has a price.