Funny you should ask.
Last night, around 11 pm, I used my 100,000 volt stun gun on a friend (with his permission).
He braced himself... set his jaw... clenched his eyes shut... cried out...
and THEN i shocked him.
He opened his eyes and said, 'THAT was it??'
I arched an eyebrow, put the gun to my own arm, and, yeah.
It felt like hitting your funnybone on a sharp corner. Certainly not pleasant, but it wasn't incapacitating.
If you're going to get one, get a POWERFUL one...