Was there something you were afraid of as a child that just seems silly to you now?
Sirens. Especially ambulance sirens, but fire truck and CD sirens would freak me, too. You see, someone (I recall it being one of my parents, in a fit of exasperation) told me at a very impressionable age that the ambulance was going to come and take me away (and I would die or never come home or something like that). For some reason that stuck with me, and I was dead scared of the sound for years.
It wasn't 'til I was second or third grade that I was cured of it. I was playing in a neighbor's back yard, on top of a rowboat that they had upside-down next to their basement stairwell. Mom had told me not to play on it, and Mom was right! I slid off the prow, right between the stairwell railings (somehow without clocking my head) and straight down eight feet onto concrete. Luckily, I landed on my arse... I apparently staggered up the stairwell steps and collapsed, gasping "get Mom"... quite dramatic, really.
So Mom called an ambulance. The driver very kindly offered to keep the siren use to a minimum, but I told him it was OK... nothing else could really bother me at that point (I remember being more in shock than in severe pain). So I went to the emergency room, where they found out I hadn't actually broken anything, amazingly enough... although I think this is where my bad back comes from.
After that, sirens were just sirens.