Of everything in the Rockies, only grizzly bears scare me more than moose. It's extremely large, powerful, unpredictable, aggressive, and can run or swim faster than any human. I've accidentally crested a hill and been almost as close as they are, and that was existentially terrifying.
When I went to Yellowstone, bison closed the road multiple times and shuffled through the cars on their daily movements. We were inches away from them, just window glass between us. Their shoulder level was the top of the car, I could see the grass bits in their fur. We were along a steep hillside, if they wanted to shove our car into the ravine, they probably could. They had young calves with them. Everyone was chill and it ended up being a really memorable experience. It's a pretty unique experience seeing an animal that can make a car feel small