I once had a teacher who (before I was in his class) had done a class experiment where he made silver fulminate, the active ingredient in those firework poppers that you throw on the ground (e.g. an extremely shock-sensitive explosive). You make it wet (in ethanol) and then dry it out on paper - but it becomes increasingly shock sensitive as it dries. It's important to not make too much at once or let it dry too thick, because even its own weight can set it off. Which is exactly what happened - and worse, it wasn't completely dry yet, so it splattered silver fulminate solution all around the room - desks, walls, ceilings, floors, everywhere. The cleaning crew was furious with him because, even weeks later, they'd be in the room cleaning and suddenly whatever they touched would just explode with a loud pop, scaring them half to death.
Also had a chem professor who did a class experiment once a week, every week, and never did a single one without some sort of safety-related incident occurring. Some were almost comic-book style, like when she was trying to dissolve a bunch of pennies in nitric acid, but they weren't dissolving, and she was talking about how sometimes the oxide coating causes a delay, and kept stirring.... then finally stuck her face right up to the opening of the flask to get a better look, right at the second that they all went off at once in a big cloud of toxic brown smoke
Also had just as awkward of a physics professor who was once demonstrating a wimshurst machine with leyden jars, which he'd charge, then discharge with a spark, charge, discharge with a spark, charge.... then set it aside. And we're all looking at each other like, "
Did he just forget to discharge the thing? Surely... he's not going to forget and then touch it later, is he?" And sure enough, 15 minutes later he needed more space on his desk, so he picked it up,
by the electrodes... there was a loud pop, then silence, and he stood there perfectly still for what seemed like an eternity. Then finally, in a quiet voice.... "
I.. think I'm okay...."
Sorry, I know, offtopic...