The most potent tool of any troublemaker in German lessons was the swastika. Our tools were a particular kind of felt tipped pen, and a 50p coin. These pens, with slow-drying ink, were used to draw a reverse swastika on the 50pence piece. Then, after finding a gullible victim, you would tell them that it was possible to test their intelligence by pressing a coin to their forehead and timing how long it took for it to fall off. If executed in a timely manner, the victim would be completely unaware that they were spending the lesson a la Charles Manson with a fucking great swastika displayed proudly on their face.