Nope, I wasn't moonlighting as a waiter at Tallywhacker's. :-P

They usually did it nonverbally and spontaneously. It was something sorority women routinely enjoyed doing to fraternity dudes. Some of the guys liked it, or didn't mind. For me, it made me feel violated...but, since I assumed they weren't doing it to intentionally be predatory, I would lightly/playfully tap them on their wrists with my three middle fingers, doorknocking-style (a "Shoo! Go away!" movement). Usually, that was enough to get the point across and get them to stop. The entire exchange would be nonverbal, on our parts. I didn't see why it should have been incumbent upon me to verbally tell them, "Stop doing that, I'm uncomfortable" when I was doing nothing to solicit their behavior in the first place (other than being male in a largely-female space).