That's not a taser, that's a "stun gun".

Tasers are effective. Stun guns are not. (Tasers are also much more expensive.)

Tasers use pulsed electrical signals to disable the target's nervous system and (temporarily, hopefully) neutralize them. Stun guns are basically just compact cattle prods, and all they do is produce some localized pain. They do not knock people out (as they're often shown doing in movies), nor do they even temporarily disable people like tasers do. They don't even really hurt that much -- if you're looking for a self-defense tool, you'd be better off with a small pointy stick -- shanking them with a pointy stick would hurt your attacker more.

The best thing you can say about stun guns is that they make sparks and loud noises, which might be able to scare/startle an attacker. That's about all they're good for, though.

This has been your self defense tool PSA for the day.

Quarterstaff. 😉

This Earthbound remake looks sweet!