https://en.wikipedia.org/wiki/Prince_Rupert's_drop
Glass + Water = pretty, decorative curio
Such an incredibly simple thing, but I can see this kind of thing fascinating people who've just discovered glass. Hell it's still fascinating now even with the knowledge of why it works like it does. Can also use the other names (Dutch/Batavian Drop) or even just a name more HnH-ish
Guy shooting the Drop with a .22 rifle to demonstrate its seemingly bulletproof properties:
https://youtu.be/24q80ReMyq0