I was debating whether to buy a case, bumper, or nothing for my iPhone 5. Then my friend sent me this: http://www.lifehacker.com.au/2012/10/repurpose-a-produce-rubber-band-into-an-iphone-grip/
Conveniently, I had a purple one nearby. It fit!
Ultimately, it stayed on less than five hours. It was a fun free experiment, but didn't seem to provide any extra functionality for me. I'm probably going to keep my phone "naked."
If you have a phone this trick will work on, give it a try!