[bvw]

I'd argue that the lightning rod and the piped iron stove are both a paired set that are the greatest -- for they saved many thousands of lives from fire.

The fire department and fire insurance is another, but those might best be viewed originally as a gang-control device as I understand.

[Liberal Classic]

Good point. I'd also say the library is right up there, too, though it's more of an institution than an invention.