This iPhone case is probably the most unique iPhone case you'll ever come across. The PopSlate is an iPhone case which as another screen on the back.
PopSlate uses an e-ink display on the back that uses very little power and can display images which are viewable in direct sunlight. It connects to an app from which you can display images on the screen. You can display anything you like such as pictures, text, websites and lots more - a GIF would be cool.
It's available for pre-order right now at $129.