Sheik

A mysterious warrior with great wisdom and strength. Sheik is a Sheikah, as revealed when he first confronts Link in the Temple of Time. He describes himself as the last remaining survivor of the Sheikah tribe. Sheik helps Link along his quest while he never reveals who he is and why he is aiding Link. His advice and knowledge of the world make him a great ally in the Link's quest.

Attributes of Sheik
Sheik Quotes from Ocarina of Time

Soundtracks/Themes
Every appearance Sheik has made in Ocarina of Time is accompanied by a melodic tune played by the harp. Titled Sheik's Theme the theme is composed by Koji Kondo and is featured in the official game soundtrack.

Ocarina of Time
Sheik reveals himself to Link shortly after Link is freed from the Chamber of Sages after a seven year imprisonment. He informs that Link must awaken the seven sages in order to bring peace back to Hyrule. Alerting him of the need to possess a new tool (the hookshot) in order to enter the temples he then disappears, later reappearing when Link arrives at the Sacred Forest Meadow. He tells Link about the warp songs used to teleport to temple entrances and teaches him the Minuet of Forest before disappearing again. Further along Sheik approaches Link at the Fire temple entrance in the Death Mountain Crater, teaching him the Bolero of Fire before walking away, using a wall of flame to halt Link's enquiring advance. More adventuring later Sheik once again mysteriously appears in the Ice Cavern to inform Link of the fate of the Zoras and to teach him the Serenade of Water and then awaits outside the Water Temple for Link to free the temple from Morpha.

Super Smash Bros. Melee
In Super Smash Bros. Melee Zelda has the option of transforming into Sheik. To do this, you must press down the analog stick with the B button. Sheik has a completely different moveset than Zelda. Sheik's moves and weapons are quick and similar to those of a ninja. Sheik is an extremely speedy character and for this reason she could be a bit difficult to control. Although she has an original moveset, she is found to have similarities with Captain Falcon. In Melee the two of them have a more powerful star rod attack. In the game, Sheik is always referred to as a female.

Super Smash Bros. Brawl
Sheik has been confirmed for the sequel to Super Smash Bros. Melee, Super Smash Bros. Brawl. Although she did not appear in The Legend of Zelda: Twilight Princess, the character model was based on a design drafted during the game's development. She has mostly the same moveset from Melee, and shares a Final Smash with Zelda, the Light Arrows.

Gender Issues
It is later revealed in the game, that Sheik is actually Princess Zelda. This would suggest that Princess Ruto's remarks about Sheik's gender are erroneous and that she was not aware of her true identity.

Various fan theories exist concerning Sheik's true gender, but the one most supported by evidence from OoT itself is that Sheik is Princess Zelda in a masculine disguise. In Super Smash Bros. Melee, Sheik's profile describes the warrior as being "she". But, if you read the Japanese strategy guide, it explains that she used magic to literally turn herself into a boy...

However, considering that Sheik was nothing more than a character, designed by Zelda to hide her true Identity, Sheik's identity would be whatever Zelda was trying to appear as. As the clothing is mainly male, Sheik can be said to be male.