Toad

Toads are the most recurring summons to be seen in the series due to some of the main characters, Naruto Uzumaki, Jiraiya, and the Fourth Hokage, being able to summon them, come from the Toad Land, Myobokuzan. Toads possess a wide range of abilities, being able to spit water or oil from their mouths and occasionally utilizing weapons in battle. They vary greatly in size; Gamabunta, the largest toad seen so far, is as big as a building, at least 100 meters tall in fact, while his two sons, Gamakichi and Gamatatsu, are small enough in Part I to ride upon one's head. In promotional artwork for Part II, Naruto is depicted riding atop an older Gamakichi, suggesting that he and his brother have gotten much bigger since their last appearances. This has been proven after Jiraiya's death, when Gamakichi and his father are visitting Naruto in Konoha to bring him the bad news. Unlike most summons introduced in Naruto, each toad is shown to have a unique personality; Gamatatsu has a fixation for snacks and Gamakichi enjoys watching battles from a safe distance. Their father, Gamabunta, speaks like a yakuza gangster who won't work with anyone he doesn't respect. Despite this, he is fiercely protective of his children and Naruto, and will fight for their safety regardless of his respect for the summoner (or, more likely, whether or not Jiraiya is on his good side). Gamaken, a toad of comparable size to Gamabunta that is introduced in Part II, spends the bulk of his brief appearance commenting on how weak and stupid he is.

The toad elders seem to hold high positions in toad-society; the Great Toad Sage, an aging and senile toad, hands out wisdom and predictions to the younger generations. He is highly respected for his track record of always being right, and getting to meet with him is considered a great honor. A married toad couple, who simply refer to each other as Ma and Pa, assist the Great Sage in his work. They also seem to be particularly powerful, as Jiraiya summons them to help him during a battle with Pain. Jiraiya speaks to both of them very respectfully, whereas most other toads he treats as his equals. Although Ma and Pa constantly bicker over such things as dinner and Jiraiya's immaturity, their combined efforts are enough to defeat three of Pain's bodies.

Known Toads

 * Great Toad Sage (Leader)
 * Shima and Fukasaku (Sages)
 * Gamabunta (Boss)
 * Gamakichi
 * Gamatatsu
 * Gamaken
 * Gamahiro
 * Gama
 * Gerotora (Key Toad)
 * Gamariki (Anime)
 * Kosuke (Deceased)

Summoners
To date, five people have signed the contract with the toads. Of these five, only the last three are known. They are, starting with the most recent signer:

The latest summoner of Toads, Naruto didn't usually summon them unless he needed Gamabunta (which ticked him off). However, upon Jiraiya's death Naruto become a sage through their methods and became more proactive with them. Naruto is highly respected among them since their leader foretold him as a "Prophesized One".
 * Naruto Uzumaki

Nothing is known about Minato's relationship with the toads but apparently he was well-respected among them. His only known summons were Gamabunta whom he called to help him fight the Nine-Tailed Demon Fox and Gerotora who holds the key to the seal of the Nine Tails on Naruto's stomach.
 * Minato Namikaze (Deceased)

The most frequent summoner of the toads, Jiraiya's techniques mainly consisted of toad based abilities. Jiraiya's nickname was even "The Toad Sage". The toads had a cordial relationship with Jiraiya, often making fun of him despite their great mutual respect. It is hinted that his preversion is the root of their jokes
 * Jiraiya (Deceased)

Trivia
Masashi Kishimoto has stated that there are a number of different types of toads; the toad that appears on the cover of volume 13 of the manga he states to be a Shaolin kung fu master. He hopes to be able to draw many of these toads for the duration of Naruto.