haha I have a story about this, did this a few times actually from when I was like 12 - 15 or so, I actually remember starting this habit.
The first time it happened, I was sitting around my basement with a bunch of my friends, and watching species, a movie which as a 13 year old boy, was very hot. I remember we were all talking about how hot the movie was, and I was saying something about how hard it made my dick. I remember there was me, 2 other guys, and a girl, and the subject of erections came up. She asked what guys did when they became "hard". My two other guy friends there just started laughing, and I said, well I jack it off. She asked me what that all entailed, and I don't know what came over me, but I said, here I'll show you. I remember my two other buddies were just shocked, one of them had actually said he never had jerked off before. By this age, I had already been jerking off for a year or two, and had been ejaculating for about a year.
So, then I pulled out my dick, which was hard as rock, and started just stroking it, leaned back and began jerking off. It was thrilling really. My friend (the chick) I remember was facinated by this, and I was telling her about how it felt and that I could shoot my semen really far too. The two other guys were at first just shocked at my boldness, but when we all started talking about how far we could shoot, I got one of the guys to join in with me.
I remember him wipping out his cock, which by this time was hard as well, sitting in the beanbag next to me, and we just jerked. I came first, and shot my long ropes of cum across the carpet, and a few moments later he came too, shooting not quite as far as me! So I won!
After that time, we had a few more times where this happened. I became kind of known in my group of friends as the "masturbator" and was actually known for just pulling out my dick and start jerking off in front of everyone on occasion. A few times, some of my friends would join in and challenge me to a "shooting contest".
Even in college I would sometimes just be sitting in the living room jerking off, and once one of my roomates actually joined me, pretty awesome experience really.
Speak Softly and Carry a Big Stick.