1. Camera+
    I still use Apple Camera App to take photos, but this is where I do my editing. With the recent addition of the 'lab', it gives you control beyond basic filters. You can also layer filters on top of each other. I manually import the pics I want to edit and then save the edited copies as duplicates to the original.
  2. PhotoFunia
    Off the wall photo shop effects. Turn your friend's baby into a zombie with a few clicks, or impose them in a modern art gallery. Literally, 400+ effects. It is a lot of fun as the name implies.
  3. Color Splash
    This is one that allows you to edit a photo to be a mix of color and black & white. I use it anytime I take a picture that has one feature that is very colorful and I want to highlight it. Takes a little effort, but the results are usually worth it.
  4. Fotoring
    Allows you to quickly place two or more pics side by side and save them as one combined photo. Comes in handy more often than you would think.
  5. Skitch
    Nice for quickly adding meme text or an arrow pointing at something.
  6. Tangled FX
    Webby tangly filters. Doesn't work well with every type of photo, but when it does work it can look extremely cool.
  7. Waterlogue
    Amazing water color paint filters. Well designed app. Very nice results.
  8. Tangent