Irish Lottery, 1992, brute force - you could purchase all ~2M combinations for < IR£1M . The company played dirty when they realised what was happening, then later changed the game when they'd finished the forehead slapping:
https://en.wikipedia.org/wiki/National_Lottery_%28Ireland%29...
There is a story similar to the dollar coin gig to earn reward miles. A long time ago when plastic gift cards were first a thing, stores didn't have a way to update the balance. The scheme would be to buy a $100 gift card from Walmart using your credit card (getting the miles). You would then use the gift card to buy a $0.35 pack of gum. Since the store couldn't update the balance, they would give you cash as change. You could then just deposit the change to your bank and pay off the credit card. Rinse, repeat.
So for $0.35, you could get $100 in equivalent reward miles. Now stores have changed, they can now update balances on the card and therefore won't issue cash as change.
To expand, this still goes on, it's just a lot more convoluted and has become quite the cat and mouse game. It's been very interesting watching how manufactured spending has evolved.
I know people used to do this by buying the $1 coins from the US treasury, and then just take the coins to the bank and depositing them in order to manufacture spending.
Look up Joan Ginther - ex-Stanford statistician and she won scratchcard lotteries multiple times (I seem to recall by arbing non-uniform geographical distribution of winning cards). Unfortunately I can't find a technically satisfying article and don't have ability to find one right now...
See also:
https://www.businessinsider.com/us-mint-ends-the-dollar-coin...