I’ve had 2 encounters… The first was an owl that was sitting in a dead tree about 40 yards from my tree. I got into my stand before first light, and just as it was starting to get light I noticed him and he took off, swung around and right towards me.
When he started getting closer I saw his talons come out and realized he was coming in for the attack.
I raised up my bow just in time to have him veer off right above my head, close enough that I could feel the wind from his wings. I was wearing a head cover at the time and he must have seen me move my head and thought I was a squirrel or something.

The second encounter was pretty comical.
I heard a rustling coming from beneath my stand and looked down and saw a porcupine heading right for my tree. Sure enough out of all the trees in the woods he liked mine the best and started to climb up. Maybe he liked the smell of my cover scent or something.
As he headed up the tree, I started dropping little pieces of bark on his head trying to get his attention, but he never looked up. He climbed up to the level of my tree stand and just nudged his head with my toe and then he looked up and noticed me there, and just started at me. I finally whispered to him “Hey, this is my tree, go find your own!”
After a couple more nudges on his nose with my foot, he decided he’d climb down and it must have taken him 10 minutes to back down the tree in slow motion. It was pretty comical to see that fool thing back down a tree and amble off.
That made my day, and makes me really thankful that I hunt and can see little oddities of nature like that!