Kingdom Hearts II/Heartless

Shadow
The most common heartless. It is pretty easy to beat.

Soldier
Can attack with a few different moves. Parry it's attacks and use Cyclone to finish off it and surrounding enemies.

Nightwalker
It is resistant to beginning magic. It is easily defeated even with the Kingdom Key.

Rapid Thruster
One of the most common enemy in the game. In large groups, use Aero Trap to defeat multiple Heartless at once. In small groups, just jump and attack.

Bulky Vendor
The rarest Heartless. It is found anywhere breakable objects (suits of armor, fireworks stands,etc). Wait as long as possible to use the Reaction Command.

Dancer
The Dancer is a Nobody that appears mostly in Hollow Bastion. It is controlled by Demyx.

The Dancer has a very effective fighting style. It will kick Sora vigorously for an extended period of times. Each kick sends Sora a few feet into the air. The most deadly attack comes when the dancer is sliding with glowing hands; if one touches Sora while doing this, the dancer grabs Sora and jerks him around in a dance before kicking him for high damage. (This is the "low posture" the journal mentions below.) They are difficult to defeat in large numbers.

They are one of two enemies that are feminine in appearence, albeit a sexy one, the other is fortuneteller.