I was 16, in science class and I was there wicked early. My science teacher was super hot and he said he had to leave the room and he would be right back. I was already horny because he is so hot. I took off every single piece of clothing including socks and shoes. I went to the very back of the class room. I sat I on top of the table am started to jerk off. The moment my load shot out of my cock, my teacher walked right back into the room. I was so embarrassed. I just sat there unable to move. I was so embarrassed. He grabbed a paper towel and said, "wipe yourself off and get dressed before the other students get in here." As he was turning around I saw that he was hard and there was a tiny wet spot where the tip of his dick was.
The boys locker room at school. There was a class tournament in my school and every class gets a classroom for the duration of the tournament. Our class had the boys locker room (actually a very nice spot, since it's right next to the sports hall, where the stage is during the tournament). I came to the locker room quite a bit before anyone else and I got bored and decided to have a wank there.
I don't know which is the craziest. I have masturbated in the woods in a park in front a female photographer and on a school yard with another male exhibitionist or in the dunes at a beach in a circle jerk.