PowerCam for iOS is sort of a grab bag of photo tools wrapped up into one free app. It takes stills and video, and offers a tremendous variety of features for the photo enthusiast.
The app includes a tilt-shift feature for miniature effects, color splash for having specific colors appear in a black-and-white image, plus cropping, rotation, collages and frames. There is much to explore, the app is easy to use and the results are good. You can even specify high or low resolution output.
One odd quirk is that the app applies filters in real time as you shoot, which seems like a strange time to do so. Once a filter has been applied, it can't be removed. I think most people would prefer to do that after the image is taken. Fortunately you can, but only after making a US$1.99 in-app purchase.