I have been summoned here so, here I go. Wow this is a great thread. I guess I would have to say, because i have been there and done that, "A tire swing."
Strangly, this happened one night while performing in Taming of the Shrew. One of the leading ladies and I got into a small tickle fight at the back of the stage. The audience laughed and thought it was part of the show. It was quick but fun.