What is the best (free) photo editing app for the iPhone?

Preferably for the 4s.

I love using Vintique. It's free and has a bunch of options for filters and other editing things.

Photo: imajicam, fotolr

If you are looking at FREE apps, then my suggestion is going to be to download several, evaluate, and choose your favorite. I mean, lets face it, you are not going to get photoshop level editing on your iphone. The apps are basically all presets, i have seen some that allow user adjustments but i haven't seen anything that I would actually use in my real work flow as a photographer, or that I would do anything with other than waste some time while I'm waiting somewhere.