Kakashi

Hatake Kakashi is the son of Konoha's White Fang. Kakashi is a genius ninja, who joined ANBU at such a young age. He became genin at 5 (youngest one ever), chuunin at 6, and was appointed Jounin at the age of 13. Kakashi's amazing trait is shown where he can excel in ninjutsu, taijutsu and genjutsu.

Kakashi was a student of the 4th Hokage, with Uchiha Obito and Rin. During his youth, Kakashi is a strict heartless ninja where he believes the success of a mission is more important than the lives of his comrades. This is because his father, The White Fang was branded a traitor and a coward for saving the lives of his comrades over the success of a mission. White Fang's action resulted in a loss for Konoha in a battle, causing the deaths of many ninjas. White Fang commited suicide because of the shame he was burdened with.

During the Battle of the Brigde, Kakashi and Obito had to save Rin who was kidnapped by a powerful ninja from the Rock Village. Kakashi finally realized the importance of teamwork and decides to help Obito rescue Rin. The enemy ninja throws a kunai at Obito, Kakashi takes the hit but looses his left eye in the process. Later in another fight they get caught in a landslide attack and Obito pushes Kakashi out of the way, his body is half crushed by the attack. He handed over his left Sharingan, which had just been awaken during their fight, to Kakashi as a present for Kakashi being appointed Jounin, just before their mission. Kakashi prevailed at the end of the battle, defeating the rock ninja by using the Sharingan.

Later, Kakashi would be known as Sharingan Kakashi or Copy Ninja Kakashi. Kakashi's formidable jack-of-all-trades ability was enhanced by the use of Sharingan, where it was said that he copied almost 1000 techniques. Copy Ninja Kakashi became a well known name in the Ninja Bingo Book, in which all ninjas are afraid or cautious of him, even among the Akatsuki's. 

Kakashi developed the Mangekyo Sharingan later in the manga series, while fighting the Akatsuki. His methods were quite different compared to Itachi, in which he uses his eye to create a rift in space and time dimension to blast his enemies. 

Since Kakashi is not of the Uchiha bloodline, the use of Sharingan and the Mangekyo greatly decreases his stamina and energy. This is the reason Kakashi always covering his left eye with his headgear.