An osprey catching trout is always cool to watch.
I saw an elk antler grown into a tree.
I watched a moose be born.
I shot a hen turkey w/ my bow this past fall, sat back down in my stand to wait for a deer. (the bird fell within sight) I look back towards my bird and there is a redtail sitting on MY turkey wings spread claiming the bird. I stood up and was able to scare him off before he got an easy lunch.

Heck I see cool stuff every time I go out.