Master Sword

The Master Sword is a legendary weapon originating from the The Legend of Zelda franchise. It is the only weapon known to be able to repent the Triforce and defeat Ganon. After its forgery, it was set in stone with the prospect that it only yields to a hero who has proven to be strong, wise and courageous.

In crossovers with the Mario franchise, the Master Sword appears along with its wielder, Link, in games such as the Super Smash Bros. titles and Mario Kart 8.

Super Mario-Kun
While the Master Sword itself does not appear in Super Mario-Kun, a sword that parodies the Master Sword called the Kinoko Sword (alongside an upgraded version called the Master Kinoko Sword) appears instead.

Super Smash Bros. series
Link wields the Master Sword in all Super Smash Bros. games, along with Toon Link in Super Smash Bros. Brawl and up. They use the sword in a multitude of moves, mostly those that are standard attacks.

In addition, the Master Sword appears in Super Smash Bros. Melee as a trophy, which can be obtained when it appears at random in one of the game's single-player modes.

Mario Kart 8 / Mario Kart 8 Deluxe
In Mario Kart 8 and Mario Kart 8 Deluxe, the Master Sword rests in a pedestal at a crossroad inside the Hyrule Castle in Hyrule Circuit. It acts as a Spin Boost Pillar, but is initially inaccessible. On the track leading to the sword, there are three spin boost crystals that, when activated, cause the sword to rise up from the pedestal along with a Dash Panel ramp that allows racers to go through it and receive a spin boost. The Master Cycle bike is heavily based off of the Master Sword.

Link also pulls out the Master Sword during two of his tricks.

Super Mario Maker 2
The Master Sword was added in the version 2.0 update in Super Mario Maker 2, where it serves as a power-up only available in Super Mario Bros. style. This item turns Mario into Link, enabling him to use his shield to block enemies and projectiles, bombs to hit switches and blow up blocks, and a bow and arrow to collect items or attack enemies. He is also able to use the sword to hit enemies, and use a dash attack with said sword and a down thrust in similar fashion to a Ground Pound. When Luigi, Toad or Toadette grab the power up they turn them respectively into red, blue and purple Links, matching the Link colors from Four Swords and Four Swords Adventures. The sprite of the Master Sword is an edited version of the White Sword from the original game.