What is the name of Zero's signature weapon?

Zero's signature weapon is the Z-Saber. It is an energy-based sword that gives Zero a close-range fighting style distinct from X's projectile-focused X-Buster.

The Z-Saber became closely associated with Zero during the Mega Man X series and remained central to his role in the Mega Man Zero games. Its glowing blade allows slashing attacks, charged strikes, and special techniques gained through battles with bosses. The weapon helped establish Zero as a more melee-oriented character.

The name is sometimes shortened informally to “Saber,” but Z-Saber is the canonical name used for Zero's weapon. Buster Shot is a ranged firearm used by Zero in the Mega Man Zero series, while Mega Buster is associated primarily with the original Mega Man. Zero also uses other weapons in later games, but the Z-Saber remains his defining armament.