Knowing that they could deliver a nasty shock, I discharged one once by shorting the terminals with a screw driver.

The sound of the spark, and the scorch mark left on the PCB and screw driver left me fearful of them.

Or was that caused by the knowledge that I had a friend who said he put one of those capacitors in a highlighter, thereby making a makeshift, single-use, "shelf-unstable" taser?

it's also interesting to witness a bit glass thing acting like a capacitor

ps: for long I wanted to make a discharge rod but never finished it