Buster Shot

The Buster Shot (バスターショット) is Zero's main long-range weapon in the Mega Man Zero series. It was originally an old model of a handheld gun used by the late Resistance member Milan. Early concept art and illustrations show that the Z Saber can be loaded into the Buster Shot as a power cell, granting the weapon the ability to be charged this way.

The Buster Shot is mounted onto Zero's back when not used.

Mega Man Zero
When Zero awoke in the Forgotten Laboratory, he grabbed Milan's weapon in order to defend Ciel and himself against the attacking Neo Arcadian troops. Once acquired, the weapon's bullets changed from regular ammunition to energy shots, and once the Z Saber is obtained, the Buster Shot's charge attack will be available with its help. In this game, Zero must use the Buster Shot extensively to earn skill points and have access to its most powerful abilities.

The Buster Shot can also be equipped with Element Chips obtained from certain bosses, adding variety to Zero's long-range arsenal. They replace the normal lv. 2 Charge Shot.

Mega Man Zero 2
Zero still has to earn skill points to level up his Buster, but there are only three skill levels, with the four bullets upgrade being removed (although Zero can still fire four bullets at a time by using the X Form). The Element Chips from the previous game return, and Zero can obtain EX Skill to use with them.

Mega Man Zero 3
In Mega Man Zero 3 and 4, Zero no longer needs to earn skill points to level up his Buster, as he starts off with all his normal abilities from the previous game. This is also the last game where the Element Chips are used. In Mega Man Zero 3, Zero can fire four bullets by using the Hacker Cyber-elf Shuthas.

Mega Man Zero 4
With the Element Chips removed, Zero only needs to earn the EX Skills from the game's bosses.

Trivia

 * The Buster Shot was mistranslated as Z Buster in the first Mega Man Zero game. The error was fixed in Mega Man Zero Collection.