A Cannon Gun, fittingly, 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 obviously 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.
Unlike most aggressive Heartless attack, it avoids you and close combat as much as possible; however, it still is going to keep you moving. Its main attack includes creating a target emblem on the floor tracking you, and fire cannon bombs (as the name implies) while you're 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 good way of finishing them quick 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.