Gamaken

is a giant toad that first appears in part II. He wields a Sasumata-like weapon and a shield. He also seems to be wearing the same robe as Gamabunta. He is constantly referring to how clumsy he is, and constantly seems nervous, albeit he also says he will do his best. He seems to be a skilled fighter while fighting alongside Naruto.

Infiltration of Amagekure
He was first summoned by Jiraiya, when he was facing the Akatsuki leader Pain, and decided to use the Hermit Mode. However in order to use Hermit Mode, it would take him some time to prepare it, and he could not afford to take the risk of leaving himself unprotected, so he summoned Gamaken. During the time it took for Jiraiya to prepare the technique, Gamaken was forced to face off with a great variety of Pain's animal summons and was kicked back and forth throughout the tower they were in, until he was pushed into a sewer where Jiraiya told him to return as he was finally finished.

Invasion of Pain
Gamaken, along with Gamabunta and Gamahiro, are later summoned to assist in Naruto's fight with Pain. They combat the various animals summoned by the Animal path until they are sent flying beyond Konoha's borders by the Deva path. He is currently lying motionless beside a mountain.