I've never had such an impulse, but I can think of at least two events where someone else was overcome with such, and did something to me. One I did not like, the other I found rather flattering.
In the first, I was showering, and this guy just jumps into my shower (no curtain or door), and goes for my cock. He's actually trying to suck me, although I'm completely soft. It took some effort to get rid of him without creating a disturbance and drawing attention
In the other, I was in the steam room, sitting on my towel. It's sort of an odd hour, so the place is empty, but there is one other guy, younger, with a VERY nice body, and quite good looking, sitting near me on the bench. Suddenly, he throws off his towel, revealing a major hardon, presses himself hard against my sweaty body, very hard against mine, and starts furiously jerking off with both hands. He sees my startled look, says "You have no idea how much I need this," and a few moments later, grunts and blasts a huge shower of cum halfway across the room, before making a quick exit.
So, I guess if you're going to sexually assault someone, at least be handsome and hot.