It can be at any price point and may even be a hostel but it cannot be a hotel that awards you points in any program other than points you perhaps get from using a credit card to pay for the hotel. The hotel itself cannot be a member of any points program. The only exception would be a hotel which has its own 'loyalty program' that rewards return visitors but cannot be used at any other hotel at all.

You can only choose one. Yes,, I know that may be very hard to do but that's the criteria you have to follow. One choice per person, your 'if I have to choose, this is the one' choice.

A brief description if you wish of why this one is your number one choice.

Include a link to the hotel's website if possible.

I have a very hard time picking just one myself but 'if I had to choose', this is the one. https://www.faulhorn.ch/en/home
Why this one? Because you have to be able to get to it to stay in it and the only way is to walk a 'fair distance'. You won't be pulling your wheeled suitcase behind you believe me. No running water (no showers), no tv and I swear the mattress in my bed was stuffed with the original horsehair brought up by mule in the 1830s. I don't think there are many hotels as unique as this one.

Buy hey, maybe you have a 5 star choice that is as unique for different reasons. What's your, 'if I have to choose only one' favourite?