Ty Roderick, Bastian Karim, Ken Summers, John Kael, Devin Franco and Rafael Carreras. I have a selection of them that always make me come, no matter how many times I've seen them.
Never happened to me once but whenever I'm on the train and its really crowded and there's a really cute guy nearby, I try to go near him and just go elbow to elbow tryin' to bask in his warmth and get hard.