Plastic Bullet is an App made by Red Giant Software, a company with many titles and large enough to actually have a sales department and a customer service department. First released a couple of months ago it unfortunately didn't save full resolution images. I, along with many other iPhoneographers e-mailed them and now version 1.1 saves full resolution. Originally reviewed in blogs as a replacement for Hipstamatic (it isn't) it is fun to use though.
Color Hipstamatic image from a couple of days ago re processed with Plastic Bullet.