Well, as Earth vs. Moon is a great game, and it is free, and it deserves publicity, I'll just post this on toucharcade. For those who haven't heard what Earth vs. Moon is: Earth vs. Moon is a missile defense game. However, it is not your regular missile defense game. For example, there are levels modeled after pong(you shoot missiles at the ball to try to knock it past the alien mothership), space invaders, breakout, etc. Note: I am not the developer.
I originally wasn't impressed with these type of games with the mistaken idea of just simple tapping on objects to shoot. But tried this and like it alot because it has more to offer then just that. I like how I can swipe the area to bring total chaotic carnage to incoming missiles all the while keeping an eye on my inventory to not deplete while trying to save my planet from being destroyed. Total destruction of my world is a sight to behold if you do lose. I just started playing but know I'll be spending some time with it. It has a lot more to the game then what I'd thought as a simple tapping game. Worth picking up.