Thermite
I’ve only ever made thermite once, at a camping trip, to see if I could. It turns out that the ingredients are very easy to get your hands on if you have a reason to go to an art supply store.
This idea came to me after an RCMP talk at a local linux meetup about how they train the police to seize digital data. You see, you can’t put out a thermite fire, and if you could make it stick to the case of the drive in question, all they could do is sit and watch as you fused your transistors into molten mater.
It seemed like the world could use this after Snowden and co.