Used to know a slightly odd, hyperactive kid in high school who used to randomly 'head-tap' my friends and I on the shoulder (with his forehead). Every once in a while we turned it into a bit of a game where you tried not to let the other head tap your shoulder. It's basically tag but arms-free (or maybe 'thumb wars' works as an analogy, for its dodgy nature)...and you can only give chase or escape by walking fast, no running.

Coincidentally or not, we were also ultimate frisbee players in middle school. And there were pogs, of course.