It scared me, but it's not scary.
I was fishing (sorry not hunting) in a stream by Chama, NM one year with my dad. The stream...we'd call it a river here...was about 1-2 feet deep and about 35 yards wide. It had some good holes in it. We were walking along, and I had just cast my little panther martin out there. Out of nowhere, something huge jumped in the water in front of me. I was splashed in the face and couldn't see for a couple of seconds. Turns out, it was a juvenile beaver. He was waddling his fat butt the other direction as fast as he could. It sure seemed huge at the time.
The second story I have is about hunting. It was just before first light, and my dad and I were trying to get into position on the edge of a meadow before the sun came up. We were going to sit and wait out the early darkness and hopefully see some elk. Well, those elk were out there alright. Something spooked them up towards us and they were on the stampede when they passed within 10 yards of my dad and I. The sky was just barely getting light, and you could see the huge bodies flashing through the trees. It was a little scary, but it was a huge adrenaline rush. That was a moment I won't forget, for sure.