Otaku Camera makes any photo look like a still from an awesome comic book. In addition to adding style to your photos, it gives you headlines about anime, cosplay, and more. It's certainly a must-have app for any anime fans.
Otaku Camera only gives you a handful of generic overlays to start with, but offers almost hundreds of new things to download in its shop. These feature your favorite characters and stills from manga and anime like Tiger and Bunny, and Berserk. During testing, everything in the store was free. That makes it seem unnecessary to have it all separate from the app's initial download. This app turns your photos into comics surprisingly well and surprisingly fast. Once it has done the work, you can do all sorts of edits like cropping and resizing in post. Once your masterpiece is created, you can share with just about any social network right from the app. You can't really take pictures from the app, though--that requires another picture-snapping app. That's the only real downside of the entire app. You won't even mind the inoffensive ads that help keep the app free.
Otaku Camera should be the standard-bearer for all novelty photo editing apps. It does exactly what you want it to do with very few negatives.