gyuudon

The Vongola Lightning Bull, appearing as a large armored bull capable of generating electricity, is the Vongola Box Weapon belonging to Lambo. It was first seen when an enraged Lambo released it with the command to kill Gokudera, who had earlier insulted him. Like all other animals owned by the Vongola Famiglia, the Lightning Bull has a crest on its forehead.

Abilities:

Cambio Forma: Lampo's Shield (Lampo means Flash in Italian): In this form, Gyuudon transforms into armor and a shield that covers Lambo's body. The shield features two horns similar to Lambo's and the Roman numeral I in the center. It also forms a helmet on Lambo, featuring the Lightning Crest in the middle and two rings encircling his own horns. This form provides incredible defensive capabilities and can fire intense bursts of lightning called Corna Fulmine (lit. Lightning Horn). These bursts are powerful enough to wipe out an entire army of Velociraptor di Nuvola.

Trivia:

Gyuudon literally translates to "beef bowl."

(Source: Reborn Wiki)