I recently designed and taught a course on future skills. For teaching problem solving skills, failing, and creative confidence I designed a Chindōgu exercise.
Chindōgu are fascinating in themselves, but even more so from a pedagogical perspective. They are inventions that don’t have a concise explanation. They aren't useful. But they aren't completely useless either. Their creator, Kenji Kawakami, describes them as "un-useless."
Chindogu 珍道具 is made up of two words. Chin 珍ちん means "curious" or "strange." Dogu 道具 means "tool" or "device."
"Strange device" doesn't quite capture the entire meaning though. There's an essence to chindogu that can't be ignored. They need to be useful, but only just so. Something people could use, but probably won't either because they are terribly embarassing or because they cause many more problems than they actually solve.
They're almost useful. Or "unuseless."
Here are some examples: