I've read a ton of scattered information (even the 2014 case list thread isn't really organized), but the selection is completely overwhelming, and I couldn't find many recommendations that didn't lack some important details.
So here are a few questions to those of you using a case with the One M8:
1. Which case are you using? how much did you pay for it?
2. How long have you been using it?
3. How many times have you dropped the phone while using the case? was the phone damaged, cosmetically or functionally (details please)?
4. Has the case scratched or scuffed the body of the phone even without dropping it? how often do you take the phone out of the case?
5. How is the grip? is the case slippery? is it easy to hold?
6. How does the case look now? did it lose its shape or color?
7. Overall, are you happy with the case? do you have anything else to say about it?
8. Have you tried other cases which you do not recommend? if so, which and why?
If you are NOT using a case, answers to the relevant questions would also be appreciated.
TL;DR Please take the time to answer the questions above, as I'm sure it will be helpful to others too.