Gamahiro

is comparable in size to Gamabunta. When summoned during Part I, he wasn't named. It was not until Part II that his name was revealed. He carries two large swords on his back.

Invasion of Konoha arc
His first appearance was in the Konoha Invasion, when Jiraiya used him to fight Orochimaru's large snakes by using Summoning: Food Cart Destroyer Technique. Jiraiya summoned him again later in the anime to help Sasame Fūma, Sakura Haruno, and Naruto Uzumaki escape from Orochimaru's hideout.

Invasion of Pain arc
Gamahiro made his Part II debut when he, along with Gamaken and Gamabunta, were summoned to assist in Naruto's fight with Pain. They combatted the various animals summoned by the Animal path until they were sent flying beyond Konoha's borders by the Deva path's Shinra Tensei technique. Of them, only Gamabunta has been seen since, though it can be presumed they are alive due to Nagato's revival of all those he killed at Konoha.

Trivia

 * He has a different skin color between the anime, where he has green and brown coloring, and the manga, where he is a bluish color. This is most likely due to him being colored in the anime before the manga.
 * In Naruto Shippūden: Ultimate Ninja 4, Gamahiro appears as a little catchable toad that is called "Professor" due to his interest in geography and such. He is not like the Gamahiro of the anime/manga - he is far smaller, sports a teacher's hat, and likes geography.