I put a matt black skin from DBrand on the back, primarily to reduce fingerprints. I also have a glass screen protector on the front.
I've ordered, and I'm waiting for a Rhinoshield Crash Guard bumper. It is a soft rubber bumper that goes around the edge of the Note5, and is supposed to give it protection from drops as high as 11.5 feet! There are numerous YouTube videos showing people testing their iPhones, and S6's with the Rhinoshield Crash Guard bumper on it, being dropped from various hights, and surviving all but those over 11 and a half feet!
Pretty impressive.
I think that this gives the phone excellent protection, while keeping it's overall thin size. For me, I hope this will be an excellent compromise between going Naked and providing some protection from when my phone will eventually be dropped!
(The Crash Guard is supposed to begin shipping October 26th, from the U.K. It's still in development for the Note5)