The "618 TYPE" paralyzer (stun gun) is a personal defense weapon of Chinese provenience. Fairly inexpensive (low 100s CZK), fairly easy to buy. See also another such one, BR-800TYPE.
The device contains a stun gun with two prods at the front, which makes a nice ~7 mm long loudly crackling spark, and a small lightbulb-based torch. The control consists of a switch and two pushbuttons; the switch connects the power to the pushbuttons and power-on LED, the buttons control the flashlight and the high voltage generator.
So, let's see what's inside.
The core of the unit is a sealed high voltage power source. This part is potentially reusable in other sorts of projects. More investigation will be done in the future.
The power for the unit is provided by nickel-hydride (maybe nickel-cadmium?) cell with 3.6V/250 mAh. Pretty low capacity.
The charging circuitry leaves much to be desired. The stepdown converter from mains 230V AC is using a capacitor and is galvanically connected with the mains, leaving the unit potentially dangerous when plugged in.
The device's downside is the quality of the soldered joints, which was outright appalling. (A typical problem of made-in-China devices.) Two of them failed shortly after purchase, by falling apart. The correction was easy, though. For tactical use I strongly suggest to resolder all the unit's joints before fielding it.