My DH is actually a very good grocery shopper. He gets the right stuff, and is very good at finding the good deals.
But once my SIL sent my brother to the store with a detailed list. When he got home, she asked him why he got a jar of pickles. He said in effect, "You wrote on the list 'fresh dill' but they didn't have fresh dills. I had to buy a jar." He had been walking around the store looking for one of those barrels loaded with pickles, that you have to pick out with tongs!