I think the only time an animal flat-out scared me was in the wilds of Rogers Park in Chicago. I was walking the couple of blocks from the No Exit Cafe back to my apartment, and a huge coal black dog materialized out of deep shadow, jumping right on me before I saw him. I didn't do anything in my pants, but it must have been because I had just emptied everything. He didn't try to bite, and his owner was right there to holler at him (The damn things name was "Devil"). It took a while before my heart slowed down, or I could breath.
My wife and I have gone backpacking, and true wilderness camping, just once, on the larger of the Manitou Islands, Michigan. We hung our pack high, way out on a rope between trees, just like the park literature recommended. We had barely settled in the tent before I heard a little clamor. Racoon, of course; I guessed him to be maybe half grown. He had scooted right out the rope to the pack, and was trying to tear into it. When he saw me, he zipped back to the fork the rope came over, but he just sat there looking at me. After a while I stepped out of sight, to get my wife out of the tent to see him, and of course he immediately disappeared. We slept with our food pack, or carried it with us, the rest of the week.