Hard Knuckle

Hard Knuckle (ハードナックル) is Hard Man's special weapon. When utilized, there is a short delay before the knuckle starts moving forward. It is somewhat slow, but has great strength. Mega Man can slightly guide the knuckle up or down once it is moving. It does moderate damage to Shadow Man.Hard Knuckle can also be used to break through Destructible Blocks in Mega Man 3 and Mega Man: The Wily Wars.

Capacity
In Mega Man 3 and Mega Man II, one Hard Knuckle uses 2 weapon energy units. It can't be used if only one unit is left. With a full weapon energy gauge, it can be used 14 times in Mega Man 3 and 9 times in Mega Man II.

Bosses weak against Hard Knuckle

 * Mega Man 3: Top Man, Doc Robot (Metal Man, Crash Man and Wood Man), Yellow Devil MK-II, Hard Man (2nd Encounter), Wily Machine, Gamma (1st Form)
 * Mega Man II: Top Man, Quint
 * Mega Man: The Wily Wars: Buster Rod. G, Wily Machine (2nd Form)
 * Super Adventure Rockman: Top Man

Bosses immune to Hard Knuckle

 * Mega Man 3: Needle Man, Doc Robot (Flash Man), Gamma (2nd Form)
 * Mega Man II: Needle Man, Wily Machine

Other media
Mega Man uses Hard Knuckle in episode 25 of the Mega Man animated series. In episode 32 of Captain N: The Game Master, Mega Man uses Hard Knuckle to defeat Top Man.

Trivia

 * The Mega Arm is nearly identical to the Hard Knuckle in that both weapons fire Mega Man's fist.