Photo editing apps are a guilty pleasure of mine. I collect them. I use them for a while, then I move on to the next one, and so on.
I have a new favorite: Pikazo. It's cool because it does things a bit differently. You give it a picture image and a style image, and it runs them through google's Deep Dream algorithms to generate something that is a combination of them both. The gallery below will show you what I mean.