MacBook Pro Retina rattling noise
Assuming your case is not the cause of the rattling issue (in other words take it off for a while and see) then this is an issue that should be brought to the attention of an Apple Store Genius near you.

The days of computers, especially laptops, making any kind of noise (barring the occasional optical drive seek noise...) is long over.

The Mac is still (essentially) brand new and under warranty and Apple needs to have a look at it.

Be advised that if they need to send it off for work they will not guarantee data on your HD stays in place. So make sure you have (at a minimum) an up-to-date Time Machine backup. Me, I'd image it (SuperDuper or CCC) just before heading out the door to my Apple Store appointment.