What was the most useless invention of the twentieth century? Explain.

The most useless invention of the twentieth century in my opinion was the cigarette holder for two. The whole concept of this invention is just awkward because of the shape and size. no one is actually going to walk around carrying a cigarette holder of that size for two people. You can only smoke one cigarette at a time so basically your sharing a cigarette with someone if you want to use it.