retromatic - retro Fun
I just picked this app up the other day. It's interface is easy and the results are fun. The only downside I see is that the it's not full-res and the brush/mask interface is a little difficult to use. Obviously, it has limited use because of the distinct look. Another one trick pony. But other than that, it's a blast! Pick Retromatic up at $1.99 in the iTunes store.