Everything. I hate grocery shopping and tend to buy in multiples so I don't have to go back or at least it's a faster trip later for stuff that will go bad.
I used to laugh when I saw that you could buy a SINGLE roll of toilet paper. Then I realized my wife's best friends mom....who is an amazingly sweet woman......and had 5 in her family and two bathrooms in her house, used to buy a single roll at a time
We went to visit once, and she asked me to pick up dish soap, and she was horrified that I bought a 10 ounce bottle, not the 1 ounce trial size. Now, MY mom used to buy small sizes of products, but she lived within walking distance of the store, and in retirement she would walk to the store daily to pick up an item or two up until she turned 89.
These folks lived 9 miles one way from the closest store, so a trip to the store was 18 miles round trip
Doh...those sales vex me. I almost never need two of whatever it is and have no excess storage space. When I am able, I get the two and donate one to the store's food bank box.
Fat-free Greek yogurt. I buy 12 cups a week. It would be less expensive to buy a large container, but I like the single-serving size for portion control.
When the kids were young, we bought a membership at a big box club just because of the price difference of the milk (cheaper at the big box than the regular grocery store). I was buying 4-5 gallons a week (3 kids and husband who also drinks milk).
Doh...those sales vex me. I almost never need two of whatever it is and have no excess storage space. When I am able, I get the two and donate one to the store's food bank box.