I found this out on a high school trip. I knew that disposable cameras just had a regular film canister inside them and one of my friends didn't believe me so I took to opening mine once I was done with it. It was the model with a flash and as I used the metal pocket knife to pry the plastic case open my whole right arm up to my neck suddenly convulsed involuntarily causing me to drop the knife and camera. I generally knew about capacitors but really didn't know enough about them to think about the possibility that it would be waiting for me. After a bit of surprised cursing, I picked up the camera and looked at where I had the knife and saw two the two leads going to the flash. Using the knife, insulated by something this time, I touched the metal blade across both leads and was treated to a loud pop and flash of light from the arcing current. The knife blade, much to my friend's chagrin, had two divots where it had arced. That was without the battery in. I then used this knowledge to add wires coming out in the shape of a taser like device and though it didn't have nearly the power to arc like a taser, it did very well to cause not-quite-skin-damaging pain to various friends at school. We had a lot of fun with that for a couple weeks.