I'm addicted to Diet Mountain Dew and nothing else will do. Even though I like the other MD flavors, I can't drink them often. Regular soda makes me sick and always has.

I'm not crazy about lower priced perfume.

Peanut Butter-It has to be Jif.

Cheese-no cheap cheese. It tastes funny to me.

Bread

Coffee

Shoes

I'm sure there are some more but I can't remember them right now.

I almost refuse to pay full price for OTC meds(Tylenol, Advil, etc.) The bargain brands are the same to me.
Many store brands are ok with me as long as they perform the same way.