Inflatable underwear.
Yeah.
Invented by a Japanese guy who was terrified of drowning. Understandable, really, as Japan is unusually prone to all manner of natural disasters such as tsunamis, etc.
So this guy made himself a pair of boxers that would automatically inflate itself on the pull of a string, expanding into a working, one - man life raft.
Not, I'll admit, the worst of ideas, but I think we can safely assume that the inventor himself would feel that the device belongs in this thread. You see, Japanese subway trains tend to get extremely crowded. Often, there's hardly enough room to move a muscle. Consequently, many Japanese people have a phobia about accidentally doing something embarrassing on board one of these trains (farting, stumbling, etc), because an untold number of strangers would not only KNOW about it immediately, but also very likely get inconvenienced, and thus annoyed.
Now, try to imagine yourself in the following situation: You are on a Japanese subway train, absolutely packed with people. You are standing in the middle of a vast crowd of strangers.
And you have just accidentally pulled the string which causes your underwear to expand to gargantuan proportions, ripping your pants to shreds in the process, and reducing available breathing space from hopelessly inadequate to nil.
Yes, this IS what actually happened. I heard they had to stop the train and pop the guy's undies with a knife.
I would guess, however, that TSUNAMIS don't scare him so much anymore!