Though the glitch known as MissingNO. from Pokémon Red and Blue allowed players to duplicate items indefinitely, it also had a terrible habit of rendering the game completely unplayable and even corrupting save files. If you caught MissingNO. inside a Pokéball by travelling along the eastern shore of Cinnabar Island and surfing next to the Pokémon Centre it would duplicate the sixth item in your inventory, including master balls and rare candy. In that respect, the MissingNO. glitch ruined the game in two ways: it corrupted your save data including your hall of fame records and it made you so overpowered that the entire experience became exceedingly pointless. I know having 1000+ rare candy sounds cool, but you wont know what to do with yourself once every challenge has been rendered obsolete, besides stop playing.