Hylian Shield
The Hylian Shield is the traditional shield of the Nintendo 64 Zelda games. The Hylian shield can either be purchased or found by Young Link in Ocarina of Time. Emblazoned with Hylian artwork, complete with an eagle and the Triforce, the Hylian shield is much too large for young Link to wield on his arm and functions more like a turtle's shell. After his seven year sleep, Link became able to use it as his standard shield (until he finds the Mirror Shield). A similar version, named the same, is used by Link in Twilight Princess and is bought from Malo Mart in Kakariko Village after dispelling the Twilight from Eldin Province. It is suggested in some media that the shield is protected by a form of magic.
Ocarina of Time
In Ocarina of Time, the Hylian Shield becomes almost necessary to survive a visit to the Great Fairy in Death Mountain, as child Link's 'turtle shell' use of the shield protects from recurrent flaming rock eruptions. It is also not prone to the risk of being burnt by particular fire-borne enemies, such as the Fire Keese. However, the shield can be lost by the shield-eating Like Likes if Link is swallowed by one. Child Link's use of the shield does not provide as much adequate protection from the front as the Deku Shield (and the Hylian Shield as an adult) and is similarly unable to reflect Deku Scrub and Octorok attacks, but it can defend Link from the stones that rain from Death Mountain. It is worth noting that the guard at the gates of Kakariko Village (leading to Death Mountain) can offer a discount in correspondence with the owner of the Bazaar in Hyrule Castle Town. Simply attempt to purchase the shield at normal price, then the shop owner will give you the discount[1]. A free shield can be found if the player opens a certain grave at night in the graveyard.
The pedestal on which the avian is perched on is often seen to be the "missing fourth piece" of the Triforce, combined known as the Tetraforce, that completes the triangle. No point in the series has the existence of a fourth piece ever been mentioned, however. This inverted triangle was presumably removed to dismiss the confusion of its such existence.
Twilight Princess
In Twilight Princess, the Hylian Shield becomes available before entering the Goron Mines in the newly established Malo Mart. It is described as a limited-time offer but will be available for purchase until Link buys it. It can also be bought (for a higher price) from a Goron in Castle Town. Its appearance is largely similar to its Ocarina of Time incarnation, with some minor design changes. It looks more weathered than before due to prolonged use over time. The metal frame is thinner now, and the numerous rivets are replaced by three large bolts. The Triforce symbol has become smaller, now with metal framing it. In contrast, the Hylian eagle is noticeably bigger and takes up the entire bottom half of the shield. The inverted triangle at the bottom has been removed and two metal decals take its place.
Similar shields
While not actually identified as a "Hylian Shield", there are various shields in other games that bear a striking resemblance to it.
Majora's Mask
In Majora's Mask, Link starts off with a shield called the Hero's Shield. The shield has many of the Hylian Shield's features, including the red Hylian eagle, the blue base, the Triforce, and the metal decals. However, the Hero's Shield features a simplified and abstract style in comparison. The eagle is either missing its head, or is facing forward rather than up. Its wings are also much larger than its body, and point down. The Triforce has moved from above the bird to below it, greatly decreased in size.
One notable difference is that the shield is small enough for Link to wield properly. This shield also appeared in the SpaceWorld 2001 tech demo for the Nintendo GameCube. Strangely enough, it is the older incarnation of Link that is wielding it.
The Wind Waker
The Wind Waker also had a shield dubbed the Hero's Shield. It's design is even more simplistic than the Majora's Mask version. The shield is predominantly brown now as opposed to the usual blue. The Triforce is in the very center of the shield. There are long swirls surrounding it as well as three bolts at its corners. A winged creature with horns replaces the bird, but unlike the Majora's Mask version, it faces up, wings spread out like the original Hylian Shield.
Four Swords, Four Swords Adventures, The Minish Cap, and Phantom Hourglass have this shield as well (or a variation of it).
A Link to the Past
While none of the sprites in-game are detailed enough to show the actual shield design, official art for both the Super Nintendo and Game Boy Advance versions of A Link to the Past depict a shield with similar qualities to the Hylian Shield.
The Triforce symbol is at the top, surrounded by two inverted triangles. Beneath it is a large, bejeweled, golden bird.
A shield similar to this one also appears in Link's Awakening.
Gallery
The Hylian Shields from Ocarina of Time and Twilight Princess and the Hero's Shield from Majora's Mask.