I attended a personal safety class in conjunction with my job. the police officer who presented it couldn't believe we didn't carry guns "I don't visit my mother in law without my gun."
She asked for a volunteer to be shocked by a "civilian" model stun gun that put out 35,000 or 50,000 volts. I hung back but my woman supervisor stepped forward. She jerked back from the instrument and scowled. The officer then passed the thing around. by then, I was not afraid of it anymore and held it to my forearm. It produced a mild tingle.
After that, I visited a couple of stun gun displays at gunshows. These ranged upward in powder to the 190-250,000 volt range.I held these against my forearm with a ball point pin between thumb and forefinger. The shock was fairly painful, left red marks and vibrated my arm considerably but I did not release the ball point pin. I''ve also held them against my leg and the sensation is far less intense. I got away from the display before the vendor decided to hit me with something more effective. I do not believe one of thse would make me fall down unless I wanted to just to encourage the user to stop.
after brusing up against a low voltage fence charger with my head, I do believe that holding one of these things to the skull would make somebody do the serious chicken.