Stun gun
Stun guns create a large high voltage spark, and are therefore useful as ignition sources. They are one of the simplest to set up, the spark gap is simply connected to the main electrodes. Stun guns provide the highest voltage of the common ignition sources, 50-900kV, but spark length is limited by the default gap. They are typically powered by one or more 9V batteries, and the trigger switch only carries battery voltage, so it can be replaced a remote trigger switch in a more convenient place. The entire stun gun circuit can also be removed from the original enclosure and mounted in a project box or similiar, though the default gap should always be left intact to prevent overvoltage and arcing. The spark gap needs to be smaller than the default gap for the circuit to function.
Stun guns are relatively cheap and very reliable ignition sources, but they are not dimensioned to be powered on for more than a few seconds at the time and could break. Most often it is the main switching transistor that dies, it can usually be replaced with any model of similiar or higher ratings.
Tasers and cattle prods also contain similiar high voltage sources, but are less well suited as ignition sources. Tasers are expensive and have a lot of superfluous components, cattle prods have a lower voltage and can only drive small spark gaps.
Stun guns are illegal in several countries, so alternate ignition sources are more commonly used outside the US. The design of a camera flash+ignition coil ignition is very similiar to that of a stun gun.
