When I was younger, perhaps about 16, I was sitting on the two separated seats at the end of an R train. A grungy looking guy sitting in the 2 seats across from me had a newspaper in his lap. He unfolded it and held it so that it shielded what he was doing from the rest of the people in the car. After that I noticed that he had unzipped his pants and began jerking off, for my eyes only. I got up and moved eventually.

I only wish this would have happened much later on in life when I had developed balls (not literally, kids). Today, I would have ripped the paper away for all to see his nasty deed and thoroughly embarrassed him, perhaps also taking the opportunity to spill a drink on him or something.

This still gives me the heebie jeebies thinking about it.
*shudder*