Your MacBook Pro, with its unibody aluminum construction, may seem impervious to most damage from everyday handling, but I've seen enough dings, scratches, and dents to tell me otherwise. That's why some choose to cover their MacBooks, whether Air, Pro, or Retina Pro, with an outer shell.
Most of these are plastic or silicone rubber, and usually fairly disposable. Covering the iconic design of a MacBook is something a lot of people would not want to do, although I have seen plenty of candy-apple-red MacBook skins in the real world over the years.
Another option is to go for a high-end shell, such as the Vaja Leather Suit. This all-leather cover fits over your MacBook Pro, offering protection while transforming the aesthetics of your laptop into something that isn't immediately recognizable as a MacBook, but has its own premium look and feel, and will at least stand out the next time you're in a coffee shop full of backlit Apple logos.
There are, of course, some drawbacks. The first is price. Vaja handcrafts its leather pieces (see one of its laptop bags in this), offering a large number of custom combinations of colors and accents.
This particular black leather version is sized for a 13-inch MacBook Pro with Retina Display, and is one of a handful of stock color options, all of which cost $270. Customized versions can take up to 30 days to make, and cost $290.
That's a stunning amount to consider for a laptop shell for most people, and several of my CNET colleagues after seeing the Leather Suit for the first time, guessed that it might cost $99 at most. Still, actually installing and using the Leather Suit, it's extremely well-made, and fits this 13-inch Retina MacBook like, well, a glove.