Useless inventions

Actually, some of them may not be such a bad idea:

Chingdogu: the not-so-ancient Japanese art of inventing ingenious everyday gadgets that, on the face of it, seem like an ideal solution to a particular problem. However, Chindogu has a distinctive feature: anyone actually attempting to use one of these inventions, would find that it causes so many new problems, or such significant social embarrassment, that effectively it has no utility whatsoever.

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