Well, its not what I'd called the scariest thing that's happened to me (that would be factual stuff such as my car crash, etc.) but in vein of what you're looking for:
a) I'd just been to see The Exorcist in cinema aged 15 (26 years ago!) and I get home, settle into bed... and something starts scratching the ceiling above me (my room was on top floor of house under attic). Needless to say this rattles me given self same incident in the movie. Eventually I (very reluctantly) investigate on my own (as I don't want to let my folks think I'm spooked after seeing the movie). After much tense creeping around in a dark attic full of boxes and old crap you can imagine my relief when it turns out its a trapped pigeon!
b) once while walking in high winds I realised something was hurtling right towards me and turned to see a metal garbage bin lid coming right at me like something from a poltergeist movie. I froze, hair on end, so shocked I didn't even think to duck... and it crashed to a halt about an inch from my face on a thin wire mesh fence I hadn't realised was there. The hairs on my neck certainly stood up for that one!
Try to be reasonable... its easier than you think...
