Shield

A shield is an item in the Legend of Zelda series that allows Link to block certain attacks from hurting him. The first shield in the series was the Magical Shield from The Legend of Zelda. The most recent is the Hero's Shield from The Wind Waker.

NES & SNES
The first shield ever used by a boy named Link was in the 1987 game, The Legend of Zelda. In it, Link automatically started the game with the shield. In this game, Link blocked attacked with his shield if he wasn't using an item or his sword. In the sequel, The Adventure of Link, Link used the shield the same way, it would reflect attacks only if you weren't using items or your sword. The trend continued into the Super Nintendo with A Link to the Past.

Game Boy
Link made his debut on the Game Boy with Link's Awakening along with a new shield setup. You acquired the shield from the people who rescued you on the island you were stranded on. Also, the shield was used when you held the button the shield was assigned to, therefore allowing certain situations where Link didn't wear his shield his at all. This trend continued in the Oracle Games (Oracle of Ages and Oracle of Seasons)

Nintendo 64 and Gamecube
Into the world of 3D, Link once again changed his shield setup. In the acclaimed game The Legend of Zelda: Ocarina of Time, the shield was bought at the beginning of the game and was used when you held down the R-Button. If you used the shield as is, Link would crouch and block attacks in that stance. If the shield was used with Z-Targeting (and later L-Targeting), Link was able to move around while blocking attacks. This system was also used in Majora's Mask. In the Gamecube game The Wind Waker, the same system was used, however, the buttons were rearranged. Z-Targeting became L-Targeting, but the shield remained on the R-Button. The Legend of Zelda: Twilight Princess is planned to be a Wii and Gamecube release, so the Gamecube controls are assumed to be the same as The Wind Waker.

Wii
Not much is known how exactly the Wii version of Link will hold and use his shield.