Chidori

The Chidori is Kakashi Hatake's first original technique, though he now uses an S-ranked version known as the Lightning Cutter. He created it around the time he was promoted to Jōnin, and later taught it to Sasuke Uchiha.

Description and Effect
This jutsu channels a large amount of lightning chakra to the user's hand. The amount of chakra is so great that it becomes visible. The high concentration of electricity produces a sound reminiscent of many birds chirping, hence the name. Once the technique is completed, the user charges forward and thrusts the Chidori into the target. This produces heavy amounts of damage that is usually fatal to humans. This technique is classified as an assassination technique because of the speed at which it is performed, despite the loud noise it produces.

As shown against Killer Bee, Chidori can also be used to simply give the opponent a large electrical shock without cutting them.

Drawbacks
This jutsu has a major drawback, however. The speed at which the attack must be done, combined with the fact that the user must run in a straight line, causes a tunnel vision-like effect for the user. This allows the enemy to easily counter the attack, making it a potentially lethal move for the user. Though this drawback would seem to make learning the technique fairly pointless, Sasuke and Kakashi are able to avoid the drawback because of their Sharingan, which take in every detail regardless of how fast the user is moving.

As an additional drawback, the large amount of chakra required limits its use to a few times a day. In Part I, Sasuke can only use it twice a day (under his own power) and Kakashi can use it four times, though their limits have been shown to have increased to an unspecified level in Part II. Should the user attempt to go beyond their limit, all of their chakra will be drained and their very life force could go along with it, killing them.

An additional problem, though not necessarily a debilitating one, is the fact that the large amount of chakra can also injure the user's hand if they put too much force into the attack. In Part I, Sasuke does this while battling his brother, Itachi Uchiha, causing some of the skin to peel from his hand and leaving it slightly smoldering after the attack was finished.

Use and Improvement
Originally, when Kakashi invented the Chidori, he suffered the drawback of the technique being a straight-line attack, which prompted Minato Namikaze to tell him not to use it, as the risk is too dangerous, and the technique would be rendered useless as the targets could simply evade it. However, after acquiring the Sharingan from his late friend, Obito Uchiha, Kakashi has eliminated the drawback, as he can predict the opponents' movements and aim at them much easier. Sometime after mastering the Chidori, Kakashi improved it to a more powerful version, the Lightning Cutter, which he uses more often than the Chidori.

Kakashi taught Sasuke the Chidori to persuade him not to use the Cursed Seal of Heaven, and emphasized the Chidori is a blade to protect his friends, as well as to forfeit his desires for revenge. Unfortunately, Sasuke has warped it into a blade to sever those bonds in his lust for power and vengeance. In Part II, Sasuke has mastered the principles of lightning manipulation, the ability to invoke the technique without needing seals and developed a number of other Lightning Release jutsu, most of which are derived from the Chidori.

Cursed Seal of Heaven Influence
Sasuke has shown by forcing more chakra from the Cursed Seal of Heaven he can use an additional Chidori after reaching his daily limit. Due to the influence exhibited by the cursed seal this additional Chidori is stronger then the standard version while essentially being the same jutsu despite it's new name of. This version of the Chidori gives off a black glow along with the sound of flapping wings in flight instead of the standard blue glow and chirping noise. While Kakashi Hatake taught Sasuke that the Chidori is a blade that protects the bonds he made with his comrades, Sasuke warps it into a blade that severs them.

Now that Sasuke no longer possesses the Cursed Seal it is presumed that he can no longer use this version of the Chidori.

Trivia

 * The name Chidori comes from a story about famous samurai . Tachibana was in possession of a famous sword called . One day, while he was still a young man, he was taking shelter under a tree, as it was raining. Suddenly, a bolt of lightning struck him. However, Tachibana used his Chidori to cut the Thunder God inside the lightning bolt, allowing him to survive. After this incident, he renamed his Chidori to.
 * Chidori can also be translated to "plover".
 * In Naruto: Ultimate Ninja 3, if you customize a few characters (such as Naruto), they will perform this jutsu in battle.