a raincoat

Someday, in a very heavy rainy season, you need a raincoat. You know someone who sells raincoats, telling you that she has any kind of clothes you need. You waited for days and suddenly she came out with a statement: "sorry, I don't have the raincoat. Would you like a jacket?" Tempted with the good design of the jacket, and a consideration that a jacket will also warm and protect you from the rain, you bought it. Guess what? It doesn't protect you from heavy rains.

You still need a raincoat.