Filters for iPhone by developer Mike Rundle, is yet another photo editing app for the iPhone that throws a claimed 800+ filters at the users for a mere $0.99. There's literally dozens upon dozens of similar apps in the App Store, but Filters works better than most of them, looks better than most, and diligently used, offers better results than most.
Filters are arranged in fairly thoughtful categories, are previewed in large thumbnails, and easily adjusted by sliding left or right. On the downside there's no masking ability, and unlike the similar, but superior Mextures, no ability to save “formulas” (only the ability to favorite a given texture for easier access later). Still, Filters is surprisingly good, and certainly well worth a look.