The dark. I was irrationally afraid of it when I was a small child. Now it’s what I can’t see in the dark that troubles me. There are significant gaps in the streetlights where I live, and if I’m walking at night in the winter I’m afraid I’ll slip on some unseen ice. I was afraid of the dark for years because I was worried Redheads from Zelda would appear. They only show up in dark places in the game!
Lightning. The town I lived in as a kid had power lines everywhere above ground and quite often during a thunderstorm if there was a bright flash of light (lightning) and the power would shut off meant it was going to be very very loud. I don’t encounter that anymore because most of the power is buried here.