shock pen

hi,
i was at a friends house the other day and he showed me his shock pen. basically it was a pen that when you clicked it it would shock you. not enough to kill you or anything but enogh shock that it jolted your thumb a bit and gave you a fright.
Anyway i was wondering how these work and how hard it would be for me to make one. I would think its probably really easy if ya know what you're doing so i figured this would be the best place to ask.
The only info about it is that it used an AAA battery.
Any advice on how to make one or any input at all is kindly appreciated.

with thanks
pj

You can use the spark maker from liters (no weal ones)

They say it make a high voltege spike output

yepp lighter will do...