Kakashi: Sharingan Warrior!

is episode 9 of the original Naruto anime.

Synopsis
With his teamwork with Sasuke, Naruto's strategy was shown unfolding. Zabuza was tricked into breaking his hold on Kakashi to avoid certain death. After Kakashi was saved from Zabuza's Water Prison Technique, he attacked Zabuza with multiple water techniques. He also seemed to copy using his Sharingan, as the Sharingan allows its user to copy a jutsu to minutest detail thus allowing him to use Zabuza's jutsu against him. Kakashi's water jutsu eventually threw Zabuza into a tree, and Kakashi prepared to finish him off, but the former was "murdered" by a hunter-nin from the Hidden Mist Village. Kakashi then collapsed from exhaustion due to the overuse of his Sharingan after the battle was over.