Painteresque
This is one of the apps you might pass by thinking it looks kinda basic. I did give it a try and was surprised just how great it actually does. 
ColorSplash
This app takes a little more time to use. Your basically turning your photo BW and adding color back to certain areas. It's not a hard app to use but does take some time to "color" your areas well.
Both apps can be found in the App Store.
