I don't know any before a certain age simply because I had no one to note or remember such things for me. I suffered from "Nth Child Syndrome" which I just made up, in which a child whose parents have had eleventy-billion spawn before them are so caught up in keeping the older ones out of jail that they take very little notice of the unique traits of the younger ones. So I am all at once bitter and sympathetic without actually feeling much of anything just at the moment.
I do recall becoming obsessed with some things from around age 10 and up. I used to write my own secret codes, sadly never anything fancy. I tried symbols sometimes but I really got interested in trying to rearrange the sounds to make something I could speak and show off to others, speaking my own language that they couldn't understand. Psh, like I wasn't already. Heaven help me if I had succeeded...
I read and reread Piers Anthony's Xanth series up to volume 8. This caused a language explosion when I was 12... I now had the adults looking up words I had used. I started drawing maps, endless maps of my own fantasy world. I must have drawn 10,000 unicorns by the time I was done with puberty.
My earliest memories, by the way, were of my baby beans doll that was my favorite when I was 3, and before that (I hope) I remember running to get a diaper (for myself) from the bottom drawer and trying to get to it first. I remember that's why I was running. I really wanted to be the first one to get there. I was, too, and I turned to the person following and that's where it stops.