Hinge
In the tree district of town you can buy a lot of tree products, including doors. With those doors, though, you always need hinges.
すう
からくり
None
You buy an awesome hinge and try it out. Instead of working properly, it just falls apart and the door falls on you, crushing your lower body. You yell out (and you have to yell) "I'm GOING TO SUUUUEEE (すう) YOU!"