Sanity Killer
You buy an AXE. Alriiiight. Way to goooo... an axe. But... the enemies are all outside. And apparently the store is locked. The manager notices your plight and agrees to help, for a price. After giving him your arm and replacing it with a robo-arm, he unlocks the door. There, the arm malfunctions and you drop the axe as the childhood nightmares leap upon you.