Vanilla essence.

A bottle of vanilla lasts a really long time. You buy it by the bottle but use only a few drops rarely. But it has to be there for those times. I feel like getting more use out of it, like making my own gourmet porridge, because fancy porridge always has vanilla in it. I googled some more ideas:

Wipe down the inside of the fridge with vanilla extract. To prolong the fresh vanilla scent, soak a cotton ball or a piece of sponge with vanilla extract and leave it in the refrigerator.

Microwave some vanilla to deodourise the microwave.

Put a drop of vanilla on a lightbulb and turn on a light: the house smells like cake.

Wear it as perfume. It will smell relaxing, or like cake.