Choco-Mog

ChocoMog is a wind elemental summon that charges or falls on and at the enemy.Found at Chocobo Ranch

Shiva

Shiva is a ice elmental queen who strikes the enemy with freezing ice.Priscilla in Junon gives Shiva

Ifrit

Ifrit is fire elemental and charges blazingly at the enemy for damage.You find Ifrit on Shinra Boat

Ramuh

Ramuh is a thunder elemental god who shocks enemies for damage.Find when you go to chocobo race

Titan

Titan is a earth being who lifts the ground itself and tosses the enemy.Found in Reactor at Gongaga

Odin

Odin is a dark warrior who slices enemies into two.Found after deafeating Lost Number in Shinra Mans

Leviathan

Leviathan is a sea serpant who dashes a large wave upon enemies.Received at the top of Wutai Tower

Bahamut

Bahamut is a large dragon who fires a flare at the enemy to kill.Found in Temple of the Ancients

Kjata

Kjata is a large animal with great elemental powers.Found in the Sleeping Forest hiding...

Alexander

Alexander is a holy elemental machine who uses holy force.Found at the Great Glacier cave

Neo Bahamut

Neo is also a large dragon who shoots great flares at the enemy in the air.Found in the Crater

Phoenix

Phoenix is a reviving summon who brings the down up.Found after deafeating Shinra at fort Condor.

Hades

Hades is a demon who cast many-a-curse on the enemy.Found in underwater Shinra plane

Typhoon

Typhoon is wind based and throws a large hurricane at the enemy.Found in the Ancient Forest

Zero Bahamut

Zero is yet another dragon who shoots the strongest flares of all.Get from Huge Blue Materia

Knights of the Round Table

13 knights who come and do massive damage each...Found on Northeast island(look at map)