I have come across
non-sexual cockslapping. (Umh, I'm not sure if some
exhibitionism was involved. It sounds very likely afterwards..)
When I was in
military service some
recruits used cockslapping in order to show their
dislike of other persons or to
punish for stupidity. A
cock was slapped on the back of stupid person or preferably on the
cheek. (However, the latter is more difficult because you have to approach a
moron unnoticed -- otherwise he will dodge.)