iPad: Pixelmator is our favourite image editor on Mac, and now it's available on the iPad with a lot of different editing features. The interface is easy to use, even if you've never really messed around with image editors before.
Pixelmator on the iPad is surprisingly similar to its Mac counterpart. You have a lot of effects to choose from alongside layers, image composition tools and all the retouch tools you'd expect from an image editor. You also get a bunch of different painting tools to create artwork from scratch. It also includes a bunch of templates to lay out photos in a variety of ways with frames and collages.
For just $6.49, there's a lot packed in here, and if you're a fan of Pixelmator on the Mac you'll be right at home when you load up the iPad version. If not, you'll be able to pick it up and get to using it pretty quickly.
Pixelmator ($6.49) [iTunes App Store]