For me, after watching Matilda, I always wanted telekinesis. I think the movie really resonated with me for other, more substantial reasons, but I remember as a kid wishing that one of my high-stress situations would let me get those powers.
Edit - Fun fact: I had a sibling who stopped believing in God because they prayed for Wolverine claws as a kid, but didn't get them.
I was this cold ass realist as a kid. I thought "wow these kids are dumb with their impossible superpowers. If I had superpowers It'd be that I'd experience time slightly slower than everyone else, allowing me to react faster than anyone and have more time to think. That would be actually possible and useful." I thought this was fully plausible because I didn't know about the nervous system.