Fire Storm

Fire Storm (ファイヤーストーム) is Fire Man's power. It fires a fireball forwards and causes a small flaming orb to circulate the user. Both the fireball and orb can cause damage.

Damage Data Chart
Damage values for the original Mega Man. 

Bosses Weak Against Fire Storm

 * Bomb Man: Mega Man
 * Cut Man: Mega Man and Mega Man: Dr. Wily's Revenge
 * Copy Robot: Mega Man
 * Wily Machine No. 1: Mega Man
 * Hyper Storm. H: Mega Man: The Wily Wars
 * Wily Machine (2nd Form): Mega Man: The Wily Wars
 * Oil Man: Mega Man: Powered Up
 * Yellow Devil: Mega Man: Powered Up

Bosses Immune To Fire Storm

 * Bubble Man: Mega Man: Dr. Wily's Revenge
 * Enker: Mega Man: Dr. Wily's Revenge
 * Heat Man: Mega Man: Dr. Wily's Revenge
 * Wily Machine (2nd Form): Mega Man: Dr. Wily's Revenge
 * Fire Snakey: Mega Man: The Wily Wars

Trivia

 * Mega Man is seen using the Fire Storm against Ice Man in the intro to the cartoon, using it to simultaneously set his parka on fire and blow him away, also defrosting a frozen area of the city. However, in the games, Ice Man's weapon is actually Fire Man's weakness. This problem also occurs in the commercial for Rockman on Famicom, not only did Mega Man defeat Ice Man with one shot from Fire Storm, this also contradict his weakness in the game itself.
 * In Mega Man Megamix, in Napalm Man's profile, it states that the scattering explosion produced by Napalm Bomb is called a Fire Storm.