LostStar Tactics is a brand new game from developer James Pawliuk, and it features one of my favorite types of gameplay. It's a turn-based strategy RPG title, so the goal here is to take a series of characters through a run of battles, controlling their movement and actions from turn to turn. There's lots of fun depth and complexity here -- each character's action is controlled by a deck of cards, and leveling up and completing matches provides more actions and more cards to play with.
The difficulty curve is well-done as well -- the game starts off very easy, but each level has quite a few difficulty levels to explore through, and there are lots of options for progression of your various troops. The interface can be a little confusing (and unfortunately this app is iPhone only for now, though it would really benefit from the iPad's larger screen, I think), but the game is a lot of fun, especially if you're a fan of turn-based strategy. LostStar Tactics is available for $1.99 right now.