Idea: If you have a vertical fridge on your countertop and you change the door so that it slides down and the cold air stays inside the part of the fridge still closed by the door, you could sort the things in your fridge by frequency of accessing them.

The door of a fridge is usually used for a lot of frequently used items. Eggs, milk, butter, and what have you. You would have to address losing that in terms of convenience and storage space.