I'm quoting my comment I made on a similar thread a few months ago.

I let a dog lick my penis when I was 11 or 12. I was horny beyond control.

I had a crush (sexual fantasy) on my good looking twink-ish friend living a couple of rooms away in my hostel. One day, when he wasn't there, so I went in (his roommate leaves a set of keys with me) and wiped my cum on his bedsheet. When I saw him wrapped in it when I dropped by their toom at night, I felt an immense pleasure and satisfaction.

I cut my pubes and put them in my classmates' algebra book. Nobody suspected me.

I peed on a rag and let the rag dry on the door handle of someone's car. When the guy came to his car, he just threw the rag away and opened the door with his bare hands and started driving like nothing happened.

IN school I went through a girl's bag and found two sanitary napkins. I took one if them home and slept with them in my underwear imagining her crotch was close to mine.

EDIT: There are some other stories too, but I've kept them for other threads.