While I was in medical school at UTHSC in San Antonio, I would study most of the night in the library. The work wasn't so hard but it took hours of memorization and reading. Whether it was the stress or just the pressure put on my cock and balls sitting still for so long, I would get massive erections throughout these study sessions.
For those wanting a better visual, my cock is on the large side of average, thick and narrow at the top. I am of average height, pretty good looking. Girlfriend's usually tell me I look like Clive Owen or MIchael Stipe. I get off to masturbating in public places and leaving my cum behind, usually dripping from a door or jizzed over the countertop. I take a piss in the sink for good measure afterward.
So one night around 1 a.m., I became aroused and went to the 4th floor restroom for my twice nightly j.o. session. There were only about three people on the floor of the library at that hour. I figure I was cool and so I took my time behind the stall door, slapping my cock on the toilet roll holder, really tugging it hard and loud. I rubbed the underside of my cock against the stall door and let my grunts come naturally. I like to spit on my hand, cup my palm and rub it over my cockhead. I was doing this in rapid circles and it made the j.o. noises only more apparent. I was so turned on by the idea of getting caught. I flung the door of the stall open and just stood there beating it hard and wild.
Finally I shot straight onto the floor just outside the stall door. It was a massive load: about five shots, the first two copious. I pulled my pants up and left the load of jizz behind on the floor without cleaning it up. I let my erection die down enough to take a piss, then I went to relieve my self in the sink. I slapped my cockhead against the sink edge and then let lose a solid stream of golden yellow piss into the basin. Instantly, the door opened (The bathroom was small - two stalls, a head, and a door right by the sink.) And in walks a younger Asian guy (not in my class, I didn't recognize him). He saw me taking a piss and quickly turned around and walked out. I zipped up and got out of their quickly, in case the campus police showed up, but to this day I relish the idea of the guy coming back to the bathroom and smelling piss and and spotting my load on the floor.
What can I say, I like to leave my mark. It feels masculine and primal to me.