Lambo's exclusive Box Weapon created by remodeling a Lightning-attribute Lightning Bull. It is imbued with the Vongola's latest technology. Its appearance is that of big, black bull covered in an armor that has the Vongola crest in it. It was the first Vongola Box to be successfully opened, when an angered Lambo it used to get back at Gokudera for his insults.
By further wrapping its body that was Solidified with Lightning Flames in armor, it can withstand any kind of physical attack. The offensive power of its horns is tremendous and that power is demonstrated even when it becomes a shield through Cambio Forma.
- Cambio Forma: Lampo's Shield: After Cambio Forma, Gyuudon takes the shape of a helmet with the Lightning symbol on the forehead section and two bladed loops by the sides and a shield with horn-like appendages and the Vongola crest with the Roman Numeral 'I' in the middle. With the difference in sizes, Lambo wears the shield around his body instead of carrying it in his arms. By using this weapon, Lambo can perform a electric attack that has a wide area-of-effect called Corna Fulmine (lit. Lightning Horn). A single strike of that technique was enough to destroy Kikyo's Nuvola Velociraptor.
- Gyuudon literally means "beef bowl."