I can top this.
Last semester I had a class in a building called University Hall. It's an old building and always seems like it's empty. Rooms are always very stuffy and the place is generally uncomfortable.
Every day, I'd use the first floor restroom before my class (around 4 p.m.). I was in classes all day, with 3:30 - 4:00 as my only break. I used my time wisely.
No one was ever in this rest room. I saw some people leaving it occasionally, as I walked past, but I was never in the room at the same time as another person. Not until one day.
It was about 3/4 of the way through the semester. The place was more stuffy than usual because the weather was getting closer to summer temperatures. The bathroom was the worst room in the building, holding in the heat and pungent smells.
So this one day, I walk in. There's a guy standing by a urinal on the far end of the room. Me, being the conscientious pisser that I am, stand to take a piss at the farthest urinal possible. I unzip, and catch this guy eyeing me up. I move in a little closer to the urinal, feeling a tiny bit uncomfortable. It takes me a while to squeeze anything out. Just as I'm about to go, the guy walks over and stands right fucking next to me, acting like he's suddenly decided to change his urinal of choice. I pinch, pull in, and zip up my pants, rushing into a stall to finish my business. The guy stands at his stall in complete silence for a few seconds as I latch the door. So I try going again when I hear the sound of footsteps closing in behind me. The guy had walked into the adjacent stall and sat down. I was sweating to begin with because of how humid the room was, but I was absolutely dripping at this point. Didn't know what was going on. I assumed the guy was mentally challenged or on drugs or something and considered leaving and searching for another rest room, but fuck, I really had to piss. But I couldn't go feeling like this guy was waiting for me! Try as I might, nothing would come of it.
Here's where it gets weird. I hear this guy shuffling around in the stall next to me. At first I didn't know what he was doing, and a moment for it to register. He was sitting in there beating off. Loudly. I shake my head, finally feeling the resistance in my bladder free up, and begin to piss. I'm looking straight down at the toilet when I feel something brush against my leg. I jump away and end up pissing all over the wall. This guy had dropped to his knees and was groping his hand through the gap at the bottom of our stalls. His left hand was just flailing around looking for my ankle while his right pounded his erect dick in my direction. He was breathing heavily. "What the fuck, man?" I said. I zipped up. I'm standing there wondering how to react when he tries crawling underneath the stall. He sticks his head through, and I kneel down and smack his face so his head hits the tile floor. He quickly pulls away starts sobbing on the toilet.
So I'm standing there like a deer in headlights, wondering what the fuck is going on, trying to collect my thoughts and figure out what to do next, when I hear the door to the restroom swing open. Someone else was coming in. The guy in the stall suddenly stops crying, stands up, walks out of the stall, turns to face me, and says "have a good day." Then he leaves.
I stand there for another fifteen seconds before taking a deep breath and leaving. Later that evening I call the campus police and tell them the story. They ask me if I can provide any details about the individual. "Uh, he was right handed. And, uh, he shaved his legs," I told them. The cop on the other end laughs a little bit and after like a fifteen minutes conversation tells me, "yeah, we've had problems there before. I'd just avoid it if I were you."
So, the point of my story? Don't take a piss in University Hall.