2360: Battle for Cydonia by Brisk Mobile is the one of the latest mech shooters available for the App Store. With gameplay that combines real time strategy and action rpgs it's a frantically paced game, though this may not be as exciting as it sounds.
With a top down RTS-inspired view point and interface, your mech uses a simple set of commands to lock on and eliminate enemies. The controls are intuitive and perfect for touch devices, which is a god-send for dealing with the hordes of enemies that are thrown at you. Drawing a path sets your mech on his merry way, while tapping enemies and the screen allows you to assign each arm to firing multiple units. There's an adjustment period for getting used to the independent firing, but you'll soon be laying down heavy fire on multiple targets easily.