1. Beansprouts. Massive 300g bag; turns to mush within a day of opening. You'd have to be cooking chow mein for a dozen people to use that quantity of beansprouts.
2. Houmous. Buy it for a buffet-style lunch. Use a quarter of it. Put it back in the fridge. Forget about it. Throw the crusty remains away after a couple of weeks.
There must be others.