Yellow/Command Materia.

Sense: Find out the enemy's HP, MP and sometimes weaknesses.
Costs 1,000 gil.
Found at: Kalm Town, Upper Junon, Midgar - playground outside Wall Market.

Steal: Steal - steals from enemies, mug - does damage while stealing from enemies.
Costs: 1,200 gil.
Found at: Kalm Town and Midgar - sewers.

Throw: Throw - throws items at the enemy to do damage, Coin - ?
Cost: 10,000 gil.
Found: Disc 2 and 3, Fort Condor and Rocket Town.

Deathblow: Deathblow - causes extreme damage to opponent or misses.
Costs: 10,000 gil.
Found: Fort Condor, Rocket Town, Jungle area near Gongaga Village.

Manipulate: Manipulate - Allows you to control one of your enemies.
Costs: 10,000 gil.
Found: Disc 2 and 3, Fort Condor and Rocket Town.

Morph: Morph - Changes some enemies into an item if it deals the finishing blow.
Found: Temple of the Ancients.

Enemy Skill: Enemy Skill - use learned enemy skills to attack enemy.
Found: Shinra Building - 67th floor, upper Junon - The Respectable Inn, Forgotten Capital,
Chocobo Sage's House - talk to green chocobo.

Slash all: Slash all - hit all the opponents with you physical attack.
Found: Ancient Forest

Mime: Mime - mimics the last attack done within the party. Counter attacks don't count.
Found: Cave in the Wutai area.

Double Cut: Double Cut - hits the enemy twice with physical attacks. 4-times cut - hits the enemy 4 times with physical attacks.
Found: Shinra Plane "Gelnika".

W-Item: W-Item - Allows you to use 2 items in one go. Found: Very southern end of the
Winding Tunnel at the end of disc 2, during the raid on Midgar.

W-Magic: W-Magic - Allows you to use magic twice in one turn.
Found: Northern Crater

W-Summon: W-Summon:
Cost: 65,000BP
Found: Available at the Gold Saucer Battle Square.

Master Command:
Found: Kalm Town travel agent - in exchange for the Earth Harp, Cosmo Canyon - if you have mastered the: sense, mime, manipulate, morph, deathblow, throw and steal command materias and have the Huge Yellow Materia.