I love the Staples TPU case. I have it for my Plus but they also have it for the 6. It is not clear but transparent frosted. I've tried so many cases that I've lost track. This frost case along with the same case in black are both awesome.
Ballistic Jewel Case (6 foot drop protection for $19.99!) is great, as is Griffin's Identity All Clear with its four feet of drop protection. Verus also makes a nice clear case: the Crystal Mixx (no drop protection claims, however).
I'm using i-Blason Clear case. Its basically everything I need in a case because its protective enough for me and not interfering with the looks and dimensions of my iPhone.