A related article: A survey of gamedevs answering "What is a thing in video games that seems simple but is actually extremely hard for game developers to make?"
https://www.ign.com/articles/turns-out-hardest-part-making-g...
https://www.ign.com/articles/turns-out-hardest-part-making-g...
Reminds me of Zelda: OoT. At the final boss fight, Ganon knocks the sword out of your hand, the only point in the game where you're without a sword equipped as an adult. In early versions of the game, if you saved and reloaded at that point, you would end up with the sword unequipped, resulting in some glitchy behavior. For example you could now use any equipped item on horseback. The hookshot could be abused to allow you to move Link pretty much freely in 3D space.
Even in later versions, you can get to this behavior by never picking up the first sword and lifting the left side of the cartridge ever so slightly when Mido blocks the way to the first dungeon until you have a sword, allowing you to pass through him. The no-sword OoT challenge is just challenging enough to be fun.
https://youtu.be/OKSWkpC_SC4?t=946 Link starts at where the master sword gets knocked off but the premise of the speedrun is interesting on its own.
To be fair, it was _saving_ after having performed the glitch that persisted glitched data to the save RAM, but I only figured that out seven years later.