Leon is a shapeshifting chameleon, Reborn's main weapon, and also his partner. Though not always seen 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-or-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 into a cocoon. After that, Leon creates an item or items for Reborn's student. For Dino, Leon created Enzo and Dino's whip. For Tsuna, he created the Rebuke Bullet and Tsuna's X-Gloves.
- Gun (Leon Shift Shape) - 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) - Leon transforms into a Magnifying Glass and allows Reborn to see someone's personality.
- Reverse One Ton- It is a one ton mallet that can remove the effects of the Dying Will Bullet to a person. He also stated that he is the only one who can use this.He only used this once on Haru and twice on Kyoko.
- Parachute (Leon Shift Shape) - 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 are Reflected, when they are supposed to petrify 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 missile and can even split into two or more Chaos Shots at will.
- So far in the anime and manga, Leon has created Enzo, Dino's Whip, Tsuna's X-Gloves, Flame Resistance Battle Suits, Dying Will Bullets, and the Criticism Shots.
- In the anime all of the scenes with Reborn holding a gun were changed from being an actual gun in the manga to being Leon transformed into a gun; this can be seen as a form of censorship as the form Leon takes makes it look like a toy gun.
- Openings Featured In: