Apple's running a "everything is at least 50% off" promotion for photo and video apps for both iOS and the Mac App Store. I'm not a big user of iOS apps for photography beyond the usual suspects - Apple's Camera and Photos app, Instagram and Flickr occasionally - the better deals are on the Mac apps:

• Pixelmator is a great Photoshop alternative at a fraction of the price.
• Flare 2 and Analog are kind of like Instagram filters for your Mac.
• ScreenFlow 5 is the best deal. A great app for editing video. It's designed primarily for recording your Mac's display to demo software but it works great as a video editor if iMovie isn't your cup of tea.