Bone Fist

Bone Fist is Jack Skellington's "weapon", as shown in equipment menu. This isn't actually a separate weapon, but Jack's skeletal hands. Due to his extended reach and height, it is not a serious pitfall. It cannot be switched to any other weapons.

Design
Bone Fist is literally Jack Skellington's fists, and is represented in Kingdom Hearts II by a grey sphere with the silhouette of his four-fingered, skeletal left hand and wrist on it.

Trivia

 * In Kingdom Hearts, Jack uses his hands to attack but in his Equipment menu it says he has "No Weapon."