The Mega Buster is a weapon created by Dr. Light and used by Mega Man. Mega Busters shoot out large balls of energy used for both defeating enemies and self defense. The Mega Buster is also used for powers Mega Man has gained.
The Mega Buster is an ambidextrous arm cannon created by Dr. Light. It can fire "Solar Bullets", which are energy bullets made of highly compressed solar energy" However, he cannot use it when utilizing a Special Weapon, due to his Variable Weapons system only allowing himself to use one weapons system at a time. In addition, its power source is a chip. Removing the chip would disable the Mega Buster.
The Mega Buster was soon upgraded by Miles "Tails" Prower to preform a Sonic Shot by shooting out large blue spiked energy balls resembling the Spin Dash to make it easier to de-roboticize the Roboticized Masters without Sonic the Hedgehog there to help.