Umezawa’s Jitte isn’t just a good equipment card. It’s not even a great equipment card. It’s a card so powerful that, during its existence in standard gameplay, many decks were forced to carry four copies for the sole purpose of canceling an opponent’s Jitte (via the old legend nullification rule).
Sword of the Samurai is far from a powerful deck by default, but just having access to one Jitte card (and five or so ways to fetch it out of your deck) can drastically ramp up the entire pile’s power. While this video isn’t the best example (due to the opponent’s bad luck), I make the case for how one little piece of legendary metal can completely turn a deck from medium-rare to medium-well done.