I always had some sort of collection on the go as a kid. Usually multiple at once. Key chains, interesting rocks, Beanie Babies, and old coins are a few I remember off the top of my head.
I think this is pretty common for children, but it doesn’t always carry over to adulthood. I won’t go as far as to say the world can be divided between collectors and non-collectors, but it does make for an interesting dichotomy.