Action Movie FX is a great app. First you take a video of something. Then you pick a certain time when you want to blow something up, make a car crash into it, or a rock hit it. You can also get new effects like a plane crashing down or a tornado. These come in two packs for $0.99 each.
Pocket Gods is a great game. You are the controller of several Pigmies. You do challenges and earn idols. Once you earn four idols you get to go into battles. You battle various gods. Then (I think) after you win you, well, you win. (But I think you can keep on doing challenges).
Jetpack Joyride is a awesome game. You fly around in a jetpack while collecting coins and achieving goals (you can also get vehicles). You can upgrade your guy by getting costumes and new jetpacks. Also, your vehicles can be upgraded. You can make them golden and make them attract coins.