A work colleague (who happens to be an ex-policeman) was on a busy train and the passenger seated next to him was browsing the Internet on a laptop. It started with fantasy gaming sites, then "glamour" sites, then men and women doing things to each other with no clothes on, and then men doing things to other men with no clothes on.
My colleague asks the guy, "Do you think you should be looking at that stuff on a train?" and is ignored.
So my colleague, who is absolutely immune to embarrassment, stands up and announces to the entire coach, "Hey everyone, this guy's looking at gay porn."
Laptop slammed shut, guy leaves train at next stop. I like to think it wasn't even his stop.