BROKEN ITEMS IN VIDEO GAMES THAT YOU WOULDN'T EXPECT TO BROKEN

I suppose a good example of this would be X Accuracy in Generation 1 and 2 Pokemon. You'd think this item would merely raise your hit rate, but in actuality it allows your Pokemon to simply bypass accuracy checks which means moves like Fissure, Horn Drill, and Guillotine go from being 30% accurate to instantly being able to destroy entire teams of Pokemon in Generation 1 or 2 if you meet the requirements for the move to hit at all.