Leon is a shapeshifting chameleon and Reborn's main Weapon. It is also his partner. Though not seen always in battle, in the anime, he is seen to be so strong that he can handle Tsuna and his Vongola Guardians and even beat them up. Leon has been shown to be able to spin threads that are resistant to Dying Will Flames. These threads were used before the Varia fight to make clothes for Tsuna that looked like his regular clothes and before the Choice Battle when they were used to make Dying Will Flame-Resistant black suits for every Guardian.
Leon also goes through a "metamorphosis". Reborn has said that Leon goes through a metamorphosis every time a student of his goes through a life-and-death battle. In the beginning, Leon's tail falls off, and he becomes unable to control the changing of his shape. At some point, he then spins himself a cocoon. After that, Leon creates an item or items for Reborn's student. For Dino, Leon creates Enzo and Dino's whip. For Tsuna, he created the Rebuke Bullet and Tsuna's X-Gloves.
- Gun (Leon Shift Shape) - Reborn uses this on the first Episode of Reborn! Reborn uses this to either shoot someone or somebody. Also, he uses this to shoot Tsuna with the Dying Will Bullet or the Hyper Dying Will Bullet.
- Magnifying Glass (Leon Shift Shape) - Reborn uses this on the first Episode of Katekyō Hitman Reborn! Leon transforms into a Magnifying Glass and allow Reborn to see someone's personality.
- Parachute (Leon Shift Shape) - Reborn uses this on the first Episode of Reborn! Leon transforms into a Parachute that allows Reborn to fly around anywhere.
- One Ton Mallet (Leon Shift Shape) - Although only shown in the anime for comedy purposes in the manga, the One Ton Mallet is described of its Ability that only Reborn can use. At will, Reborn can lift and swing this Weapon around as if it were as light as a feather and if Reborn hits someone with it, not only will their Dying Will Flames will be extinguished, but it can also be used just as a normal Weapon.
- Reflect Mirror (Leon Shift Shape) - While conducting his own Trial, Leon transforms into a Mirror and Reflects all and throws back the attack to the enemy. Even the Sky Flames is to be Reflected when its suppose to engulf everything.
- Chaos Shot - While conducting his own Trial, Reborn with his partner Leon fires a set of Sun Flames that numbs all the body's organs and nearly shuts them down making the body act as if it were dead. It acts as a homing missle and can even split into two or more Chaos Shots at will.