Gamabunta

is the chief of the toads of Mount Myōboku. He is usually summoned for battles with the largest of enemies. At first, Naruto could only summon him with the Nine-Tailed Demon Fox's chakra. Without it, Naruto could only call upon some of Gamabunta's smaller children. Gamabunta was first seen in the premiere of the series, where he and the Fourth Hokage faced off against the Nine-Tails. He is not given a speaking role until he was first summoned by Naruto.

Personality
Gamabunta is a grumpy and highly apathetic toad. He does not like to take orders from anyone, unless the summoner is highly talented and earns his respect. Jiraiya, Naruto and the Fourth Hokage are three of the few people that he has allowed to ride on top of his head without question. While he is quite confident of his abilities as a fighter, he is well aware of his limitations and perceptive of the power of his enemies, shown in his reluctance to confront tailed beasts (the Nine-Tailed Demon Fox and the One-Tailed Shukaku) head-on.

He uses some Japanese words that only a yakuza gangster would use, but he is portrayed as an ultimately powerful and positive force. He is fiercely protective of his kin, where in one instant only decided to fight Shukaku after hearing the opponent attacked his children despite believing it to be suicidal only moments before. He hates to be underestimated by anyone, both of which take precedence over his normal apathy. Often, it is one or a combination of these two factors that entices him to fight.

Overall, despite his grumpy exterior, he shows sympathy to Naruto as if he were a son. He even explained to Jiraiya that he was aware of Naruto's talents and potential. He and Jiraiya seemed to be good friends and, as implied in the series, drinking buddies, despite Jiraiya's admitted lack of control over Gamabunta. However, he would scold him on occasion.

Abilities
In all his appearances, Gamabunta has been shown to be a powerful fighter, regardless of whether or not his summoner is by his side. Gamabunta also exhibits a wise and knowledgeable demeanor, as seen during the fight against Shukaku, where he demonstrated his extensive experience by ordering Naruto to forcibly awaken Gaara.

Taijutsu
Despite his great size, he possesses surprising agility, as shown when he leapt out of the crevice that Naruto had first summoned him to, reaching several miles above the ground before crashing back again into the forest. Gamabunta showed great skill at fighting in mid-air a number of successive kicks. Gamabunta's arsenal includes a large tantō, which he can wield to inflict colossal damage with due to his immense size and strength.

Elemental Jutsu
Gamabunta is a water release user, able to "spit" water ninjutsu such as Water Release: Gunshot out of his mouth, making a formidable force against Fire Release users. As well as "spitting" water jutsu, Gamabunta can also spew oil from his mouth for use in a synchronized collaboration jutsu, called the Fire Release: Toad Oil Flame Bullet technique, in cooperation with his summoner. While his summoner prepares a fire jutsu (or another source of ignition), Gamabunta will prepare a mouthful of oil to fire out of his mouth at high pressure. When Gamabunta is ready, he will shoot the oil out at the target while his summoner, (Jiraiya or Naruto), ignites the oil. The oil, acting as an accelerant, fuels the fire, creating a conflagration of far greater magnitude and force than the original fire ninjutsu had used.

Chūnin Exam Arc
When Naruto first summoned Gamabunta while falling to his potential death, Gamabunta didn't believe that a little kid like Naruto could have summoned him. Naruto, angry at the comment, claimed that, as Gamabunta's summoner, he was the toad's master. This made Gamabunta lose his patience with Naruto, and he threatened to kill him. This scared Naruto into submission, but he vowed to become the toad's master. It was not until Gamabunta saw the summoning contract scroll that he believed that Naruto had actually summoned him, although he was not overly surprised by the fact, indicating that he had known that Naruto was indeed the one who had summoned him all along, and that, otherwise, the boy wouldn't have persisted to gain his respect. After Naruto passed out from riding on Gamabunta whilst trying to make the toad his, the toad boss took Naruto to the hospital, leaving his footprint as a signature.

Invasion of Konoha Arc
During the attack on Konoha, Naruto summoned Gamabunta to save himself from being crushed by Gaara's Sand Waterfall Funeral. Gaara was in his full One-Tailed Shukaku form, although Gaara's personality was still dominant at the time. Gamabunta was his usual grumpy self, and refused to fight for Naruto.

Naruto demanded that he show him the respect he was due as his follower. This only further annoyed him, prompting him to claim that he couldn't take him seriously- remarking that Naruto was 'too young to share sake with him.' Then Gamakichi, who had been accidentally summoned by Naruto earlier, told his father that Gaara had tried to kill him and that Naruto had saved him. Gamabunta was impressed with Naruto, and he officially accepted Naruto as his subordinate, declaring "I'll show you plenty of honor-bound duty!" as he drew his tantō.

At first, Gamabunta was able to hold his own, but this quickly changed when Gaara forced sleep upon himself, allowing the Shukaku to take over. Due to Gaara not being asleep for very long, the Shukaku hadn't reached full power. Despite this, the Shukaku proved to be too much for Gamabunta to handle. However, Naruto and Gamabunta used a Combination Transformation to take on the form of a giant fox (in the anime it was in the form of the Nine-Tailed Demon Fox), allowing Gamabunta to get Naruto close enough to Gaara to wake him up by punching him. Gamabunta was once again impressed with Naruto, and even lamented that he would not be able to see the end of this battle because he had reached his limit and had to return home.

Search for Tsunade Arc
During the battle between Jiraiya, Tsunade, and Orochimaru, Gamabunta was summoned, along with Katsuyu, to counter Manda. Finally having a chance to face each other as enemies, Manda and Gamabunta exchange threats to kill the other. Manda first attacks Katsuyu, but Gamabunta uses his tantō to protect her. When Katsuyu was free, Gamabunta used Fire Release: Toad Oil Flame Bullet along with Jiraiya. However they both noticed that Manda merely shed his skin and attacked them from under the ground. Gamabunta held Manda's tail while Tsunade, using Gamabunta's tantō, impaled Manda through his mouth, effectivly ending the battle.

Land of the Sea Arc
In the Land of the Sea, Naruto summoned Gamabunta to battle against Umibōzu. Gamabunta wasn't happy about being summoned in seawater (toads are freshwater creatures), but fought anyway because he was underestimated by his opponent. The sea water also gave him a rash. He and Naruto defeated the otherwise indestructible water creature by evaporating it.

Gamabunta then threw Naruto into the air as punishment for summoning him in seawater. However, he noted that he was still happy that Naruto took so much care of his children.

Invasion of Pain Arc
Gamabunta made his Part II debut when Naruto was informed of Jiraiya's death.

Gamabunta, along with Gamakichi, Gamaken, Gamahiro, Fukasaku and Naruto were later summoned to Konohagakure by Shima to assist in the fight against Pain. They combated the various animals summoned by the Animal Path where Gamabunta silenced the large dog summon after he landed on top of it. After Naruto used his Wind Release: Rasenshuriken technique he began to run low on Sage Chakra but still wanted to take out one more Pain before he ran out. Seeing as the three toads were being pinned down by the many summons, Gamabunta swallowed Naruto and the Animal Path, so that Naruto could kill it without the disturbance from the other Pains, while Gamabunta kept off the remaining Pains.

After he spat out Naruto and the Animal Path, the summons disappeared, but Naruto was also out of Sage chakra now. Seeing this, the Deva Path saw his chance to attack and even avoided Gamabunta's attack with his knife, landing right in front of Naruto. As Naruto fought the Deva Path, Gamabunta called for Naruto to get out of the way as Gamabunta himself would attack, only for Naruto to tell him the same as he would go into Sage Mode again and did not want him to be caught by his Rasenshuriken. Although Gamabunta still attacked, the Deva Path avoided the attack once again.

After Naruto killed the Naraka Path the Deva Path finally recovered it's gravitational manipulating abilities and pushed the attacking Naruto away. Gamabunta and the other toads proceeded to attack Pain with their weapons, but he easily avoided them. The three toads then tried to attack Pain again, but he appeared in the middle of the three and used his Shinra Tensei to send them flying out of Konoha's borders.

As he lay sprawled on the forest, he stated that it felt like all of his bones were broken. Gamabunta was later seen seemingly unconscious on the road back to Konoha by Neji with his Byakugan, who referred to Gamabunta as one of Jiraiya's toads. He told Team Guy that Pain had attacked Konoha when they approached him.

He was later seen back on Mount Myōboku. There he had been wrapped up in bandages on his entire upper body and arms and sat together with the Great Toad Sage who used the Telescope Technique to watch the outcome of the battle with Pain and the discussion between Naruto and the real Pain, Nagato who then uses the rest of his powers, in turn sacrificing himself, to revive the people he killed during the invasion. When the Great Toad Sage said that it was over, Gamabunta asks what was going on and the Great Toad Sage tells him what had happened was foretold, though the prophecy child had been both of Jiraiya's students, and saying that maybe it was all meant to be once Jiraiya decided not to give up and that the first book he wrote really was the key to changing the world.

Naruto Shippūden 2: Bonds
Gamabunta made a small but comedic appearance at the end of the movie. While Gamabunta was sleeping, Jiraiya summoned him to cushion the fall of Naruto and Amaru that would have otherwise killed them.

Naruto Shippūden 3: Inheritors of the Will of Fire
Gamabunta appeared in a non-speaking role as Jiraiya's mount when he shielded the Sunagakure ninja envoy led by Gaara from an avalanche, halting potential conflict between them and Konohagakure.

Trivia

 * Gamabunta wears the kanji (蝦)　for "shrimp" or "ebi" on the back of his kimono of sorts. Ebi, when used with another kanji　(蝦蟇), turns into "gama", which means toad.
 * Gamabunta's being a toad summon that helps human warriors was probably influenced by the Ôgama (大蝦蟇（おおがま）) stories and pictures during the Edo period.
 * Gamabunta has a prominent scar over his left eye. In the manga, this scar was not present in flashbacks to Jiraiya's training with the toads. However, the scar does appear in the anime adaptation.
 * Gamabunta makes an appearance at the end of Naruto Shippūden episode 9 omake by squashing Naruto and Sakura when Naruto summoned him.
 * Gamabunta survived battles against two of the tailed beasts: once against the Nine-Tails, summoned by Minato; and once against Shukaku, summoned by Naruto.