Sheikah

The Sheikah are a secretive, magical race devoted to the Great Goddesses, as is believed by some Zelda fans. They swore loyalty to the Royal Family of Hyrule, perhaps due to their religious convictions, as the Princess of Hyrule oftentimes functions as a sort of "priestess" of the Goddesses. It is implied by Nintendo that most of the Sheikah died off in a forgotten war.

Characteristics
One of their characteristics is the eye color. Most members of the Sheikah tribe have red eyes and sometimes even the sheikah logo, an eye with the tear drop, on their clothes. Often the character from the figures is mysterious and calm. The manga (which should not be considered canon) states that the logo used to be just an eye until there was a traitor in the Sheikah tribe. The tear was then added.

Members of the tribe
One of the most famous Sheikahs is Impa, Zelda's caretaker and the sage of the Shadow Temple. Sheik also claims that he is of the Sheikah tribe, but later in Ocarina of Time it is revealed that Sheik is indeed Zelda, who disguised herself as a Sheikah.

During the games series there appear lots of characters who can be identified as Sheikah. Kafei from Majora's Mask has the remarkable red eyes as well as the old lady from the Hidden Village, which is the former home of a tribe that protected the Royal Family of Hyrule in Twilight Princess. Magicana, the scryer in Twilight Princess has this eye color plus the sheikah logo on her forehead. Also in Twilight Princess, Renado, the Shaman of Kakariko Village, seems to have Sheikah characteristics. Even in Wind Waker there seems to be a sheikah, the only human mailman on Dragon Roost Island has a big sheikah logo tatoo on his back, although his eyes and character don't seem to fit.