Back in college, a bud and I walked into the bathroom at a party and stood at the urinals. A moment later, the door opened and a girl came in. She leaned against the wall by the other guy and watched us both as we peed, with a smile on her face. I had cock and balls both pulled out, and leaned back to give her a good look. She grinned at me, then reached down and slipped her hand around the other guy's cock. He started growing hard immediately.
At the time, it seemed the best course of action was for me to leave the room, as we were in a frat house and I didn't need to get some drunk yelling in my face. The other guy, for his own reasons, left the bathroom right after me.
Looking back, all I can think is "What a couple of idiots."