The Provost T1 (Piston Provost) had a crowbar slotted into the side of the right hand seat. My instructor would often break it out and use it to wop my head.
Fortunately, we had bonedomes.
Later, when instructing on Chipmunks, I had a stude who would always raise the nose of the aircraft when turning left. I was able to reach far enough forward to poke him sharply in the back of the neck when he did this. He developed a technique for left turns which included leaning forward. He couldn't escape the "reeling in" procedure, however, which meant my grabbing his R/T pigtail and pulling him close enough to give him an appropriate rattling.