Frozen dinners.
16 oz bottled soft drinks with a bottle deposit.
Margarine (I can afford butter).
And the big one:
Price tags. Some supermarkets used to have labels, but I remember one store where they had the price directly imprinted with ink. I had a relative that operated a restaurant and often they just bought stuff from a supermarket since the price was good (especially if on sale) compared to a restaurant supply store. But some items for resale might have that inked price on it, and they'd just use rubbing alcohol to remove it.