F'donk
When a dude yanks his junk out and whaps it on a girl's face like it's a punishment. The noise it makes is *F'donk*, and it's loud enough to wake the dead.
My teacher did this to a student. The whole class laughed so hard they fell out of their seats.
My brother did this to his girlfriend. She turned red and kicked him.
A guy in the mall did this to a girl. She ran out screaming.