I accidentally speared a small lithium ion battery with a screwdriver a few years ago. A small one, about an inch square and 1/4 inch thick. It started burning immediately and I fortunately had a clear space to pitch it to and let it burn out.
I fly quadcopters all the time (thanks to the media they're now referred to as drones). A couple of years ago, I had a bad cell on one of my 4 cell LiPos so I needed to dispose it. I know how to properly do it but figured this was a good time to show my wife just what they are capable of. I had my wife come outside and, from a distance, shot that battery with a pellet gun. Now she understands.