Who is your favorite summon?

Shiva: the queen of ice, the beauty shiva takes many forms, and freezes her foes with Diamond Dust

Ifrit: A flaming beast, Ifrit's form has changed over time from a giant to a burning feral beast.

Ramuh: The thunder lord, Ramuh actually takes speaking roles in several FF's, he is the wisest of the summons

Bahamut: The king of dragons, bahamut is the second most powerful summon, and takes many forms, form bahamut to bahamut fury

Leviathin: The king of the eidolons, Leviathin is married to Ashura, and is a giant sea serpent who attacks with waves of monumental size

Ashura: the wife of Leviathin, she heals and guards her summoner and protects her people with her all seeing gaze

Sylph: a farie that uses an ariel drain

Anima: a chained monster whose true strength will never be known. He controls the underworld.

Magus sisters: these three irritating sisters are always arguing with the summoner. They serve the wind archfeind

Valefor: A wind drake, valefor has an evolving limit break that makes him very dangerous

ixion: A thunder horse

Odin: a man who rides on slepnir the six legged steed, Odin cleaves his foes into peices and hefts the gungir lance

KOTR: the most powerful summon, the 12 members of the round table strike as one to eliminate all foes, and King Arthur finishes with a blow from excalibur

atmos: "the gateway" atmos inhales and sends entire castles to other dimentions. Alternately, Atmos uses gravity damage to crush his foes

Carbuncle: this ruby headed fellow casts reflect on the party to protect his masters

Pheonix: the only summon who has the power to grant life, Pheonix burns away its foes while reviving its masters

Doom train: this guy is a literal train who rams his enemies

arc: an airship turned monster, arc eliminates his foes by attacking them with everything he's got

mog: he makes your materia better and rides chocobos

chocobos: kick and stomp and kweh kweh kweh

alexander: guardian of alexandria, he is the holy avenger

Titan: the earth giant

belias: the flame giant

mateus: the dark angel

ultima: the queen of magic, she rules over even leviathin and bahamut

gilgamesh: if you don't know gilgamesh, you should leave

typhon: ultros's best bud, the unintelligable wind man

there are others, but I wont list them, you can