Another one that to me is equally impressive: instant glues

https://en.wikipedia.org/wiki/Cyanoacrylate

The first thorough research went into them when looking for new clear plastics, and this route of making them was ruled out because it would rather stick to everything than ease the production of objects with nice optical properties. The story goes, it was so annoying to work with that it was initially shelved, and only years after being considered again and ruled out again for a different project, the utility of its reliable and fast bonding was fully appreciated.