I once heard Marc Cuban say the best investment an ordinary person can make is to buy things in bulk when they are on sale. Say you normally buy detergent one bottle at a time. If you catch it on sale at 20% off and then stock up for the year you are going to get a 20% return on your investment which you'll never achieve in the stock market.

Made a lot of sense to me. I stocked up on butter when it was 4 dollars. I filled a couple of shelves in my freezer. I just got done with that batch and saved a ton of money.