As a kid, I had kid fears - darkness primarily.
I wouldn't call this irrational, as it's based in personal experience. As a kid about age 3-4 I followed the neighborhood kids into the woods looking for a kite. I got tired and sat on the dirt pile that wasn't a dirt pile. A few moments later I'm back at the house screaming with ants going in and out of every orifice of my young body. Dad's telling me to strip down and get in the tub, and I'm defiantly refusing because his buddy is there and I'm not getting naked in front of him. The fear that lingers today, though to a lesser extent, is of bugs getting in my eyes, ears, nose. Drives me to fits of finger digs and nose blowing.
Jaws kinda killed my interest in the beach. Not a great fear to get as a kid growing up in Florida. I don't enjoy any body of water anymore. Gator horror films, despite how cheesy they may be, combined with too many in person encounters in lakes around G'ville cured me of wanting to swim in either place any more.
I blame Stephen King's "It" for one that stays with me. Building upon the kids fear of the dark, a read "It" and forever have issues walking around street sewer drains.
More grown up fears that linger, and are irrational IMO, would be two. Over the years I developed a fear of heights. Growing up, no worries about doing any stupid thing, at any height, on any flimsy structure. Now, I'm laying flat down on my belly holding the kids by their belts as they lay on their bellies to look out over the edge of a cliff. Used to be I'd walk around the edge of it no worries. I think this is also parental fear about keeping the kids safe at all costs, but I was over the top in dealing with it and personally have no interest in being in tall buildings anymore. The second comes back to sewer drains, but it is more a fear of dropping anything while walking over them. I've always been one of those people who over thinks 'be safe', but I avoid walking over regular water drains in parking lots and elsewhere for fear I'll drop my keys or phone or wallet. I stare intently as I walk by sizing up the openings to decide if the phone would fit, and if I'd be skilled enough to kick it across the parking lot as it fell. Stupid fear, but I haven't dropped anything in there yet!