Needle Jizō

Jiraiya uses chakra to harden his hair and shape it into spikes, which are as sharp as metallic weapons. His hair also grows long enough to wrap around him, serving as armour. Jiraiya can use this technique to discourage opponents from attacking him, or activate it in response to physical attacks they've already started, causing them to impale themselves on the spikes. In the anime, the hair is resilient enough to defend Jiraiya from arrows. Though useful, Needle Jizō does not fully cover Jiraiya, leaving areas of his body vulnerable to attack.

Trivia

 * is the Japanese name of the bodhisattva Ksitigarbha. He is considered to be the guardian of children and travellers and the saviour of those who have to suffer in the underworld.
 * In Part II, Chōji Akimichi grows his hair in a similar way when using Spiked Human Bullet Tank.