As with an iPhone, a case is almost a requirement when you get a new macbook. As much as it can hurt to have to put a case over your brand new stunning laptop, it will not hurt near as much as it will if you end up dropping your laptop. Personally I would recommend having your case before you even get your macbook!
A Security Lock
Similar to a bike lock you can get, you can get smaller more portable ones for laptops. If you are planning on using your laptop while going to school, or while in public, getting one of these can prevent you from never seeing your laptop again. Even if you are just running to the bathroom while your laptop is on the desk, that could be enough time for someone to walk by and take it. If you have a lock that you can connect to the table, you will have nothing to worry about.
USB SD Port/CD drive
Since your laptop most likely did not come with any type of SD card reader or CD reader, it can be handy to purchase portable ones that can be plugged into USBs. The SD card can be useful for things such as images from your camera. A CD drive can be useful for things such as installing games or programs, watching movies, or listening to CDS.
We all already have enough cord’s in our lives, with our laptop chargers, phone chargers, etc. So I recommend getting some wireless peripherals that can make your life easier. If you do not like your keyboard on your computer, or you plan on using your computer while connected to a tv/monitor, a wireless keyboard can let you type on your computer while it is on the other side of the room from you. A wireless mouse I would definitely recommend, as they are often much easier to use then the trackpad that comes with the computer. I would also recommend wireless headphones if you listen to music or watch videos while away from home.