UniWar tips its hat at both the StarCraft and Advance Wars series with three playable races that each have slightly different advantages and disadvantages while waging a turn based war on a hex grid.
We loved the game when it was introduced as it was one of the few asynchronous online multiplayer games available on the iPhone. The game now supports push notifications so you know when it's your turn.
If you somehow missed picking up this game so far, now's the perfect time while it's free.
App Store Link: UniWar, Free (Today)