Biggoron's Sword

The Biggoron's Sword is an enormous blade crafted by the immense Biggoron. It appears in several games as an alternative to the one-handed Master Sword. It is obtained from Biggoron in several games as the ultimate goal of a trading sequence.

Ocarina of Time
In Ocarina of Time, the sword is a much more sturdy version of the Giant's Knife, which Biggoron crafted for a certain carpenter. It is the the reward for completing the Adult Link Trading Sequence of the game. This blade is much longer than the Master Sword, and it must always be wielded with two hands, meaning that Link cannot defend with a shield while wielding it. However, the damage dealt by the Biggoron Sword is much greater than that of the Master Sword.

Oracle series
In Oracle of Seasons and Oracle of Ages, the Biggoron's Sword can only be acquired in a Linked Game by use of a password. In Oracle of Ages, the sword is obtained from the Goron Elder who resides at the Goron Shooting Gallery. In Oracle of Seasons, it is obtained from Biggoron himself. While every other item in these games is assigned to one hand and can be used in conjunction with another, the Biggoron's Sword takes up both slots as it is held with both hands. Link swings it in a whole 180-degree arc, as opposed to the other swords' 90-degree slash.

Receiving this sword, along with many other items, is entirely optional, and will not affect the main plot.

Soul Calibur II
The Biggoron's Sword made a return as a sub-legendary weapon for Link in Soulcalibur II. Although very powerful in this game, it is wielded with only one hand and thus drains Link's health with each swing.

Trivia

 * In Ocarina of Time, the Biggoron's Sword is incapable of defeating Ganon's beast form as only the Master Sword can deliver the final blow. However, it can be useful during the battle, as Ganon knocks the master sword out of reach. Having an extra sword after this makes the battle significantly shorter and easier.
 * The sword is said to be extremely heavy, which is why Link wields it with two hands. This makes it odd that Link would need to wield it with both hands, if the Golden Gauntlets allow Link to lift heavy objects that can be over 2x his weight.
 * Although the shield cannot be used while the sword is out, Link attempts to protect himself with the blade with the R button. If Link does not have a shield due to a Like Like, he cannot do this, oddly enough.
 * Although Biggoron's sword is supposedly unbreakable, Link receives it as the Broken Goron Sword.