Mirrorgram
There are a ton of photo apps for the iPhone, but Mirrorgram by StageBloc Inc. is different from the rest. With Mirrorgram, you can add a mirror image to any object in the iPhone's camera lens, but this isn't just a simple mirroring trick as it can produce stunning kaleidoscope-like images. The app isn't just free, but is also easy to use and you see what's happening in real time.