Define "neatest". Do you mean most unique? From your post title I assume you mean most memorable (meaning good and memorable!)

Unique - opening the tent door to a moose staring at me only feet away.

Every sunset and sunrise is "neat" to me - I am a sunset junkie. Best sunset of the year was at Point Reyes national seashore.

Not seeing a single person in 5 days.

The neatest thing that I did NOT see: a grizzly bear, thank goodness! Four weeks in grizzly country and I was relieved not to have to deal with that.

A "neat" but sad thing- visited the snout of a glacier that I have been to over the years. It has retreated over a quarter mile in the last 30 years.