The Cannon Gun is shaped like a small cannon. Its body is blue with cyan highlights and silver rivets. It has four short, sharp, silver legs, a large, silver spike on either of its sides, and a black base. The Heartless's face is a black sphere with glowing yellow eyes set in the front of the cannon's body. The actual barrel of the cannon is black and has several red designs that cause it to resemble a face, with the mouth of the cannon being the nose. It also sports a short, curled, red fuse in its back.
In Kingdom Hearts II Final Mix, the Cannon Gun's body becomes orange, the highlights pale yellow, all the silver pieces become dark brown, and the barrel becomes dark steel blue with yellow designs on it.
The Cannon Gun's name references the weapon it was modeled after. The word "gun" can also refer to types of cannons. Its Japanese name, "Aiming Cannon," has a similar meaning, and may reference the targeting reticule that appears when it fires. "Li'l Cannon" emphasizes its small size when compared to some of the similar Heartless introduced in Kingdom Hearts 358/2 Days.
Kingdom Hearts II
Cannon Guns avoid Sora and close combat as much as possible; however, it still is going to keep him moving. Its main attack includes creating a target emblem on the floor tracking Sora, and fire cannon bombs if not cautious. Get in close or use magic to destroy the Cannon Gun before the bomb lands. Cannon Gun can be an annoying enemy, especially when paired with aggressive Heartless, since they are good attack supporters.
A quick way of finishing them is to cast Magnet on attract them and finish them of with a strong spell. Alternately, changing into Wisdom Form and sniping from afar is also a good tactic, since Sora can move while attacking in this form. Also, Sora is considerably faster in normal form as well, so it may be chased after.
Kingdom Hearts 358/2 Days
Li'l Cannons can be a threat if left at a distance, so it is advised to quickly close the distance and interrupt their attacks with physical combos. Magic is also a good options, as they are severely weak to all forms of magic (except for Fire, which they absorb), but make sure when casting that there's enough time to dodge any of their fireballs that may be coming down.
When targeted, wait until the bomb is about to land, then make use of Air Slide or Dodge Roll to avoid the attack. Proper timing is needed, as dodging too early or too late will result in getting caught in the blast radius. Also watch out for when it aims itself forward, as that signals a fireball that will fire straight forward. Unlike the targeted attack, however, the direct fireball can be blocked.