The Master Sword

"But then, when all hope had died, and the hour of doom seemed at hand... a young boy clothed in green appeared as if from nowhere. Wielding the blade of evil's bane, he sealed the dark one away and gave the land light."

- The Legend of Zelda: The Wind Waker

The Master Sword is typically the most powerful weapon in a Zelda game for general usage. The master sword will usually have a power level of two or three unlike the starting sword.The sword is said to be forged many years before the Rise and Fall of Ganondorf, although it's exact origins, and makers are unknown.

Ocarina of Time
This legendary blade resides in the Temple of Time. To gain the Sword, Link, must collect the three Spiritual Stones, and use the Ocarina of Time to open the chamber where it is sealed. The Master Sword is the key to the sacred realm that holds the Triforce. In both Ocarina and the Wind Waker, the Master Sword locks away evil from Hyrule, when removed from it's resting place its prime purpose becomes to attack and reseal evil and restore peace to the world.It can go back in time it power are unknown.

A Link To The Past
The legendary blade that rests in the Lost Woods of northwestern Hyrule in a pedestal with ancient Hylian inscribed on it, which says the hero with all three Pendants will wield it on cataclysm's eve, reading: "The Hero's triumph on Cataclysm's Eve wins three Symbols of Virtue. The Master Sword he shall then receive, keeping the knights line true." This blade has the power to emit a beam from its blade to attack enemies from a distance and has a power level of two. The Master Sword is also called "the Blade of Evil's Bane", and has the power to repel evil magic.

The Wind Waker
The Master Sword is predominately referred to as the Blade of Evil's Bane in the Wind Waker and rests in a hidden chamber in Hyrule Castle, deep beneath the waves of the Great Sea. The Master Swords use as a key to lock evil away is broken when a young Link foolishly draws the blade, he awakens Ganon´s army from their ancient slumber. Later Link Learns that the Master Sword (After Ganon killed Fado and Laruto, the last sages of the sacred realm that remain after the great flood) has lost its power to repel evil and Link must awaken two sages in order to regain that power.

Twilight Princess
The Master Sword within Twilight Princess is located deep within the Faron Woods in the Sacred Grove(the ruins of the Temple of Time. The blade is said to once be held by the Legendary Hero.  It is the one relic that allowed Link to break the curse that Zant places on him after the end of Lakebed Temple.  The Master Sword in this game also allowed Link access to other numerous hidden temples later in the game (like the Temple of Time). The sword's locations marks a link between A Link to the Past and Ocarina of time, as it resides in the Temple's ruins, a place that is notably similar to the sword's resting place in ALttP.