Final Fantasy VII/Enemy Skills

Enemy Skills are special attacks used by enemies.

The characters can learn the enemy skills by having the Enemy Skill materia equipped when the monster does the attack. The skill can only be learned if none of the currently equipped Enemy Skill materias have the skill. Frequently, the most effective way of learning the enemy skill is to use Manipulate on creatures that know the skill. After the skill is learned, they're used by choosing the E.Skill combat option.

(To add: all of the completely useless enemy skills =)

Aqualung
Causes water damage on all enemies. The most obvious enemy to learn this from is Jenova-LIFE.

Bad Breath
Recommended The signature attack of Malboros, which in FF7 can be found in Gaea's Cliff. This incredible attack adds the enemies many nasty status conditions.

Beta
Causes fire damage on all enemies. Can be learned from Midgar Zolom.

Big Guard
Essential. Same as Barrier, MBarrier and Haste on party. Look for Beach Plugs near Corel/Gold Saucer/Gongaga region - Manipulate them to get the skill.

Magic Breath
Recommended. Causes multiple different types of elemental damage (Fire, Ice, Lightning) on all enemies. Generally speaking, blows the paint layer off most of the enemies. Can be learned from Stilvas in Gaea's Cliff.

Magic Hammer
Recommended. This enemy skill makes the target lose 100 MP and the character gains it. Using this a lot makes some magic-based enemies far less annoying, especially ones that rely entirely on magic.

Trine
Causes lighting damage on all enemies. Can be learned from the boss Materia Keeper, or the Stilvas in Gaea's Cliff.

White Wind
Essential. Cures status ailments and heals each party character for as many hit points the using character has.