Final Fantasy VIII/Guardian forces

Quezacotl
Quezacotl can be obtained in the First Disk of the game. Once you gain control of Squall in his classroom on the second floor, log on to Squall's study panel in the back of the class. Select the option Tutorial and the GF will be automatically received. If you disregard the study panel Quistis will give you Quezacotl upon exiting Balamb Garden.
 * Element: Thunder
 * Special Attack: Thunder Storm - Thunder damage to all enemies.

Shiva
Shiva can be obtained in the First Disk of the game. Once you gain control of Squall in his classroom on the second floor, log on to Squall's study panel in the back of the class. Select the option Tutorial and the GF will be automatically received. If you disregard the study panel Quistis will give you Shiva upon exiting Balamb Garden.
 * Element: Ice
 * Special Attack: Diamond Dust - Ice damage to all enemies.

Ifrit
How To Obtain Defeat Ifrit at the end of the Fire Cavern.

Element Fire

Special Attack Hell Fire - Fire damage to all enemies.

Siren
The Siren, a quite powerful GF can be drawn (using GF draw ability from GF junction) from Elvoret during the fight with it on the communication tower (disc I) before escaping from indestrustable X-ATM092.

If you have forgotten to draw it from Elvoret, you can draw it from from Tri-Point in the Wind Cellar of the Ultimecia's Castle (disc IV).

It's special power is "Silent Sound" that causes a little non-elemental damage against enemies (rarely on bosses) plus 'silence'.

The Brothers
Special attack: Brotherly Love

Sacred lovingly catapults Minitaur skyward after lifting the ground from under his foes. The two collide in air.

Deals earth damage to all enemies.

Diablos
How to obtain: Use the magical lamp from Headmaster Cid.

Name of move: Dark Messenger

Move type: None ( damage done determined by Diablos' level)

Useful Abilities: Mug, Enc-None, Time Mag-RF, and ST Mag-RF

Carbuncle
How To Obtain: After Edea makes her speech in Deling City, two creatures will melt from stone on an adjacent building, jump onto the ground, and leap behind rooftop where the speech took place. Draw from any of the two Iguins.

Special Attack: Ruby Light - Casts reflect on all the party

Useful Ability: Auto-Reflect

Leviathan
How to obtain: Draw him from Garden Master NORG after opening the pod or Trauma in Ultimecia's Castle if you missed it.

Special attack: Tsunami

Deals water damage to all enemies.

Pandemona
Pandemona can be obtained by drawing from Fujin, during the battle with Fujin and Raijin in Balamb.
 * How To Obtain

Tornado Zone - Absorb all enemies into a bag attached on left shoulder, and blow them out. Does wind elemental damage to all emenies.
 * Special Attack

Spd-J: Junction spells to Speed. Spd+40%: Automatically increase character's gauge bar filling speed.
 * Useful Abilities:

Cerberus
How to obtain: Approach him during the raid in the Galbadia Garden and defeat him.

Special Attack: Counter Rockets, casts Double and Triple to all active members of the party which allows a party member to use a spell twice or three times in a row.

Alexander
How to obtain: Draw from Edea(second fight) at Galbadia Garden or Catoblepas in Ultimecia's Castle

Special Attack: Holy Judgement

Doomtrain
How to obtain: Have the Solomon Ring, 6 Steel Pipes, 6 Remedy+, and 6 Marlboro Tentacles in your inventory and then use the Solomon Ring

Special attack: Run away train

Deals non-elamental damage to all enemies

Bahamut
Bahamut, King of Dragons.

How to obtain: Defeat him in the Deep Sea Research Center, chose "It's not our will to fight" for "So you wish to challenge me?", "Never" for "Begging me for mercy?" and the hidden option for "Damned imbeciles. Why do wish to fight?". You will also fight 2 Ruby Dragons minimum, only if you answer the first two questions right.

Special Attack: Mega Flare

Jumbo Cactuar
How to obtain: Defeat the Jumbo Cactuar on Cactuar Island

Special Attack: 10,000 Needles

Tonberry King
How to obtain: Defeat the Tonberry King, found by defeating around 20 Tonberries in a row in the Centra Ruins

Special Attack: Chef's Knife

Eden
How to obtain: Draw it from the Ultima Weapon at the bottom of Deep Sea Research Center or from Tiamat at Ultimecia Castle

Special attack: Eternal Breath

Odin
How to obtain: Defeat him in the time limit at Centra Ruins

Special attack: Zantetsuken

Gilgamesh
How to obtain: Obtain Odin before going into the Lunatic Pandora and fight Seifer.

Special attack: Zantetsuken, Masamune, Excalibur or Excalipoor