Adobe Photoshop is great for professionals but it's also very pricey. For $29, Pixelmator is Retina-ready and makes it easy to edit photos, including Photoshop images with layers. This app lets you remove unwanted elements from your photos, correct wrinkles and zap red eye with a click. Plus, Pixelmator includes 150 filters and special effects. In addition to iCloud support, the app lets you share images via Facebook and Flickr.