Advanced Bloodline Limit: Sharingan
The sharingan is a special eye ability "doujutsu" that is in the Uchiha clan. It is in the pupil of the person's eyes. It is said that the sharingan evolved from the Byakugan. The Byakugan is far more superior. The sharigan greatest strength is the ability to see and copy nin and genjutsu's.
The sharingan does require chakra to activate yet it does not require hand seals to be performed. The user must focus chakra into his/her eyes. But to use the sharingan effectively, you have to combine it with other types of diverse jutsus. For instance Kakashi uses the sharigan ability to read the opponets movements inorder to effectivly use the Raikiri.
The sharingan's main ability is the copying of other jutus. It will copy any ninjutsu, genjutsu. The movements of the opponent can be copyied and predicted by studying him or her carefully. The sharigan will copy any jutsu with or without the users knowlege which makes the "doujutsu" very helpful in battle.
The sharigan has a few weaknesses. It uses up a lot of chakra. With the ability to unconsciencly copy jutsu techniques and the ability to read opponents movements and use genjutsu by looking at the opponent alot of chakra is exhausted during a fight. The sharingan also is weak aganist speed. Taijutsu is a dangerous enemy to the sharigan. Since taijutsu is based on the opponets own physicallity the sharigan can only copy stance not follow movements. Combining taijutsu and speed will give an advantage over the sharingan. The speed and techniques used in taijutsu arent chakra related but have alot to do with the opponents stamin and physical prowess, because of that the sharigan can read the movements but does not help the user react due to lack of training in taijutsu most sharigan holder have.
Mangekyou Sharingan is the Uchiha Clan mastery bloodlimit. Unlike the Sharigan the Mangekyoou Sharigan is a greater form allowing the user to mimic any genjutsu and ninjutsu and counter it to effect there opponent. The greatest strength of the Mangekyou Sharingan is the ability to omit a powerful genjutsu that will cause great physical suffering to the opponent with just eye contact. There has said to be 2 users of this Mastery Bloodlimit, Uchiha Itachi being the only known. Inorder to gain this ability an Uchiha Clan memeber must have great mastery of the sharigan and be willing to kill the person they consider to be their dearest friend.