Usually when something like that is happening to you, you are too busy surviving to be scared; the fear comes later. One day we decided to take the little girls to the zoo, and we went to the Zoo in San Francisco. During our walk around the place, we found out that they were going to have feeding time for the big cats. On the grounds of the zoo is a stone building of classical design. When you walk into it you are in a large room ringed with cages built into the massive walls. These cages are actually the back "rooms" of the big cat habitats. They open the inner doors and the lions and tigers (no bears) surge into the inner cages, and they feed them. I was standing there and you are so close to the caged cats and they are SOOOOO huge. I had an instinctive and very strong urge to flee, and flee rapidly. I could barely control it. The fear was so sudden, instinctive and strong. Must be a genetic remnant from more primitive times - very interesting. I think it had something to do with being in a room with the massive beasts instead of out in the open where you are free and they are caged.
Another time I was bikeriding on the trail and came to a bumpy stretch. My bike started to fall over and as I glanced down I saw the rattlesnake right there where I was going to fall. Actually, I don't really remember what I did or why I didn't land on the snake. I think I briefly put my foot down to keep from going over. The snake was not there on the way home. Snakes do not terrify me, but rattlesnakes one does not mess with.
The Nightstalker was scary. He was a crazy home invasion sort of robber who killed anyone there just for the hell of it, I guess. He is the reason we have the lock on the sliding glass door. He would strike all over the bay area, no rhyme or reason. He's the one they caught eventually in L.A. when the neighborhood people spotted him and chased him down, in a fury at being scared and having to have their windows all locked up during the hot summer weather. They beat him up and handed him over to the police, who have him to this very day. What was his name???
When I was a teenager the scariest things that happened to me were the times my mother would drive down to San Diego with the aunts. I would worry the whole time she was gone and imagine all sorts of traffic accidents etc. Nothing ever happened though except for the time they could see the glow of a grass fire on nearby hills so they stopped and called the highway patrol to see where the fire was so they would know in what direction to head to avoid it. The CHP told them the fire was centered right where they stopped to call - so obviously they left in a hurry.
But really, the scariest things are those that threaten the people you love instead of those that threaten yourself.