Neji Hyūga was a member of Team Guy, and considered the genius of the Hyuga clan.
Neji had the unfortunate luck of being born into the branch house of the Hyuga clan. I say unfortunate because this fact prevented him from ever being anything more than a servant to those from the main branch family. This fate was solidified when his cousin Hinata turned 3, and Neji was branded with the Huyga Main Family's Juinjutsu, a cursed seal that signified the subservient nature of the marked. It was also a seal that would automatically protect the secret of the Byakugan if the marked Hyuga were to be killed.
Neji grew up hating his relatives because when he was younger, his father sacrificed himself to protect his older brother, Hiashi, the head of the Hyuga clan. This happened because when Hinata was young, she was kidnapped the Head Ninja of Kumogakure. The kidnapper, however, was intercepted by Hinata's father, Hiashi, and was subsequently killed him. It was then demanded, as per the treaty between Konoha and Kumogakure, that Hiashi's body be handed over. Seeing this, Hizashi (Neji's father), volunteered to take his brother's place so as to protect his village, his clan, his brother. Neji, however, grew up thinking that his father had been forced to do this and thusly resented the main family for it (I mean who wouldn't?). After finding out the truth, however, Neji did a complete 180 and became fiercely loyal to the Hyuga clan, especially his younger cousin Hinata.
The first time that we really see Neji is when he faces off against his cousin Hinata in the Chunnin exams. He brutally defeats her both attacking her mentally and physically. His anger boils over so much that he tries to deliver a killing blow, only to be stopped by the jonin sensei watching over the match. This enraged Naruto so much that Naruto swore to defeat Neji in the Chunnin Exam finals.
In his match against Naruto, Neji again attempts to break Naruto's resolve the same way he tried with Hinata. Naruto, however, fights Neji to the end and ultimately uses some deceit in defeating the Hyuga genius. It was at this time that Hinata's father, Hiashi, apologizes to Neji and tells him the truth about how his father died.
After this even, Neji's entire demeanor in life changes. He quickly ascends to the level of Jonin, and is considered one of Konoha's best. He is then seen extensively in the Sasuke retrieval arc. He matches up against Kidomaru. While fighting against Kidomaru, Neji realizes that he is outmatched. Using his intellect, however, he devises a plan where he allows himself to be pierced by Kidomaru's arrows in order to locate his opponent, debilitate him, and take him out with Gentle Fist. The fight, however, brought Neji to the brink of death.
The next real time we see Neji is during the battle against the ten tails. Neji rushes up to the front of the lines with his uncle Hiashi and his cousin Hinata. Together the three Hyuga defend their comrades and give Naruto enough time to enter Sage Mode. The Ten Tails, however, launches an attack directly at Naruto, and as Hinata launches herself to protect him, Neji launches himself over his cousin to protect both her and Naruto. Neji, accepting his death, just tells Naruto that he chose to protect him because Naruto had called him a genius. He also tells Naruto that Naruto's life is not only Naruto's but also his cousin's, Hinata's life, and his own as he was willing to sacrifice himself for Naruto.
Frankly Neji, to me, was one of the kindest and most noble of all the Naruto characters. After learning the truth of his father, he was willing to die for his friends a moment's notice, as evident by his death. He also continued to not only develop his immense skill, but also his loyalty and compassion for others, especially his cousin Hinata. I wish he had survived.