Magic Mirror
The Magic Mirror is an item given to Link in The Legend of Zelda: A Link To The Past when Link travels to Death Mountain. He acquires the Mirror by helping the lost Old Man find his way to the safe house on the mountain. (Note: This man will replenish Link's life energy each time he visits him in his house.) Link is able to use this magical mirror to travel from the Dark World back to the Light World. Once returned to the Light World, he can go back to the Dark World by touching the sparkling "X" point that appears where he returned to the Light World. This "X" can also be located by using the map. The Mirror is essential to getting to the Tower of Hera, the third dungeon in A Link To The Past.
One more function of the Magic Mirror is that it can warp Link back to the beginning of any dungeon if he uses it while inside. This is comparable to the the function on Manbo's Mambo in Link's Awakening.
In legend, it is believed that while in the dark world, you look into this mirror, and you see yourself as you should be (because without the moon pearl, you change shape).
Four Swords Adventures
An ancient mirror found in the Temple of Darkness in The Dark World. It looks like any other ordinary round mirror.
Ganon steals this along with the trident and uses it to cause havoc and create Shadow Links. It is also said in the storyline that it was used to seal a dark tribe, similar to the Mirror of Twilight. Whether this mirror has any connection with the Mirror of Twilight, is unknown.