The list of summons that characters currently have.
Cats: Includes a wide variety of felines as part of the pact and are noted for their speed and grace. It is rumored that they have an affinity to fuuton chakra.
Snake: Snake summons range from small vipers the length of one's forearm to monstrous snakes that are larger then most buildings. Known for their venom and cunning, they can sometimes be a difficult summon to control.
Raven: Black carrion birds, it is hinted that a raven summoner is able to see what their ravens see and hear. Primarily they are scouts and psychological implements.
Insect: Insect summons range from maggots to cockroaches and possibly include other kinds of insects as well. Some require human sacrifice to call and they are known for a hard shell.
Dragon: Each of the dragon kinds is directly related to one of the types of basic elemental chakra, and each dragon summon can make for a very potent ally if used properly. However, only the strongest shinobi have ever been offered a summon pact with the dragons.
Mongoose: Not much is known about mongoose summons at this time.
Tiger: The tiger clan is one of the most powerful summon clans. They are extraordinarily powerful, single minded, and many can use powerful lightning techniques. However, they are often rather direct in their means of dealing with problems.
Centipede: The Centipede clan is swift and agile, and also quite resilient. They use primarily Earth and Genjutsu techniques.
Bats: Bats are used as scouting and stealth implements. They are known to be made up of primarily fruit bats, but do have some vampire bats. They have an affinity to Yin chakra.
Weasels: Weasels are intelligent, quick, and deadly. Most of them are notably wind-aligned, often being used to augment wind attacks. They're also notable for small size; the Boss Weasel, Itachi, is only 6'6" tall, being essentially man-sized. The next largest few are about 5' tall. Most are perhaps twice the size of natural weasels. Many use weapons; sickles are a favorite.