We Just Don’t Do That
Think of something which you have seen other people doing, but which you would never do yourself. Write a story whose main character does that very thing. Try to convey why in that character’s eyes, his or her actions are justified or worthwhile.
The behavior doesn’t have to criminal or morally reprehensible. It could also be an act that strikes you as tasteless, tactless, foolhardy, tedious, etc..