/k/, what do you keep in your shotgun's tube?

I hear a lot of people put different kinds of shot in their tube for different purposes - birdshot, buck, buck, slug, shit like that.

It's something I never understood really and it seems like most people do it just because they can. You can't determine what kind of ammunition you will need in any situation; if you are defending the inside of your home and the immediate area around it, you should only need some good quality buckshot. How do you know that your third shot is going to need to be a slug when it could just be filled with buck? If you are fighting at a distance then keep plenty of slugs on hand, or you can just use Federal tactical buckshot which hardly spreads. If you are engaging a target further than that, we aren't really using a suitable weapon.

Explain what you keep in the tube, the order, and why.