In Ultima Online, you could buy all the house deeds from a vendor. The way they coded the economy, this caused demand to go up and you could then resell them to the vendor for a higher price. I stayed up for over 24 hours making millions doing this. The kicker was that gold actually had weight. You couldn’t move with 100k gold on you. You had to drop your gold on the ground, move a few spots, pick up your gold, and drop it a few spots in front you all the way to the bank.

To this day, I look for economy exploits like this in every game I play.

The legend of Zelda: A link to the past randomizer. Every seed is a puzzle.