Upon finding out I was a musician in high school and college, people would ask me, "Which instrument do you play?" For years, I answered, "the bass," but realized later that a lot of people assumed I meant the electric bass. Then, I started saying I played the double bass. Even though that terminology is correct, it always sounded peculiar to me; it made it sound as though I played two basses at once. At a certain point, I started saying I played the upright bass, and more people understood what that meant. Still, for clarification, people would sometimes ask, "You mean that big bass that has to be lugged around?"
That's the one.