Stun guns and taser guns only work on peole who don't have much tolerance for electric shock.
I was "making" stun guns when I was 12 or 13. All you need is a transformer (any type that comes out of a stereo, cell phone charger, etc) then you attach a power source to it in reverse polarity, a capacitor (those little things you find in most stereo or electronic equipment, especially older stuff) and bam, you have a stun gun.
If it's not powerful enough, either try a different transformer or increase the # of batteries to produce more power.
The most I've done, when I was about 17, was 4 9-volt batteries (most stun guns have 1 or 2, and make from 40,000-80,000 volts). It hurt like a motherfucker, but still didn't knock me out. I'd like to try a taser if anyone has one.