Been using no case since the 5 (only had a 4s before that). Some fare better than others. My first iPhone 5 got bang'd up so badly that eventually the headphone jack didn't work anymore so I had to pay to get a replacement (expected). At the time, it was $50 so a no-brainer when friends had cases running more than that.
My current iPhone 6 is kinda rough. The corners are banged up a bit and there's a nice little wear spot on the back where it rubs the surface of whatever it's on unevenly because of the camera.
Oh and all up one side is a series of scratches. I have no idea how those happened but I think I accidentally put my keys in with my phone one time. I'm not sure how it could have done all of those so maybe that's not it...
I always tell the story of my iPhone 4s that I babied, made sure I got a pristine one, babied some more, put it in a case, and retired it (gave it to my wife) who had it stolen about a month later. Gone.
Right around that time, my office tried to implement a "no cell phone in the secure area" policy that was laughable. I decided it was far stealthier to carry without a case and plus, who cares? You can baby it all you want and one bump into the pool or whatever and it's done for anyway...
I was set on getting white/silver this time and then they introduced the matte black. Slate of my iPhone 5 had been my favorite so far (though the 6 and 6s black with space gray was a nice change) so once I saw matte black, I was sold.
