Thunder Beam

Thunder Beam (サンダービーム) is Elec Man's Special Weapon. When used by Mega Man, it shoots three long electrical bolts in different directions, one forward, one straight up, and one straight down. Because of the three-way spread and the ability to go through enemies, Thunder Beam is considered the most powerful weapon in the first Mega Man game for NES and Mega Man: Dr. Wily's Revenge for Game Boy. It can also break certain barriers that can otherwise only be removed by the Super Arm. In Mega Man Powered Up, it can be used to charge certain blocks. In the NES version of Mega Man, it can make short work of the Yellow Devil and other bosses when mixed with the "pause glitch", allowing to hit them multiple times with one shot. The Thunder Beam makes an appearance in Mega Man 10, as it is used by one of the Weapons Archives.

Damage Data Chart
Known damage values for the original Mega Man. 

Bosses weak against Thunder Beam

 * Ice Man: Mega Man and Mega Man: Dr. Wily's Revenge
 * Yellow Devil: Mega Man and Mega Man 2: The Power Fighters
 * Copy Robot: Mega Man
 * Iron Ball: Mega Man: The Wily Wars
 * Wily Machine: Mega Man: The Wily Wars
 * Dive Man: Mega Man 2: The Power Fighters
 * Wily Capsule: Mega Man 2: The Power Fighters
 * Time Man: Mega Man: Powered Up

Bosses immune to Thunder Beam

 * Bubble Man: Mega Man: Dr. Wily's Revenge
 * Enker: Mega Man: Dr. Wily's Revenge
 * Flash Man: Mega Man: Dr. Wily's Revenge
 * Heat Man: Mega Man: Dr. Wily's Revenge
 * Quick Man: Mega Man: Dr. Wily's Revenge
 * Wily Machine: Mega Man: Dr. Wily's Revenge