So, here's a dumb one.
I was making a batch of thermite (You know, as you do) so I could test some precision application. I've wanted to see if I could burn through a lock using thermite, but the application of the compound is really messy and it doesn't do well against gravity. My idea was to thread thermite, and a phosphorus strip around a string so that it could be more precisely applied. My first test, I put the phosphorous strip in the string, and then just kinda coated the string in thermite.
I placed the thermite in a little plastic box in case it went crazy, and I lit the phosphorous strip.
The thermite didn't react at all. Which is not what is supposed to happen. But I could see smoke in the box. So I basically had something of a bomb in my backyard. And water does NOT help in this situation.
Being the brave little dumb-butt I am, I got closer to the box to see what was going on. Then the box popped, shattered, and the thermite spontaneously ignited. Right in front of my face. I'm lucky I didn't get a scratch...