Useful household item, offensive weapon, or both?

[tggzzz]

Not necessary to find and select a strobe mode. All that's necessary is to sweep the focussed beam across the eyes. Even a "startle effect" would be significant, and possibly sufficient.

ISTR being taught in school physics lessons that sparks were ~10kV/cm. Can't find that in my copy of Nelkon's textbook.

[Zenith]

ISTR being taught in school physics lessons that sparks were ~10kV/cm. Can't find that in my copy of Nelkon's textbook.

I'm sure I read that in "Introduction To Atomic Physics" : S. Tolansky.

Probably a good enough rule of thumb. It must depend on all sorts of things such as humdity, atmospheric pressure, the shape of the electrodes etc.

[AVGresponding]

The strobe on those things is unpleasant, especially if your eyes are dark adjusted and you don't expect it. It might disorient an attacker temporarily. You also have to cycle through the modes to select it. i'm highly sceptical of some of the claims I've seen made for it. They remind me of those newspaper ads from years ago for products which ridiculous clams were made for; x-ray specs, torches with hermetically sealed electrical energy which would last for ever, a disc that would enable you to hypnotise people at will.......

Static shocks can easily be tens of thousands of volts. A 10kV shock from a car door on a hot dry day, and a 10kV shock from a 1µF capacitor, would be very different things. Once again I'm doubtful about the effectiveness of those torches with shock baton features. We can safely dismiss talk of Mega Volts.

The "grill ignitor" modules are full-fat taser modules. I expect the loophole to be closed, eventually, maybe.

You need a spark gap to limit the voltage, Big Clive has played with a few and recommends no higher than 15mm or the voltage climbs high enough to damage the module itself.
I ran mine off a single LiFePO cell, with a 10mm gap, and it gave fat, fast, loud sparks. You would not want to be on the receiving end.