Shadow Blade

Shadow Blade (シャドーブレード) is Shadow Man's primary weapon. The Shadow Blade is a large shuriken that can be shot in 5 different directions (left, right, diagonally up and right, diagonally up and left and straight up). In Mega Man 2: The Power Fighters, the directions are reduced to four, being unable to shot straight up. The Shadow Blade has a relatively short range, as it boomerangs back.

Capacity
Two Shadow Blades can be used by one weapon energy unit in Mega Man 3 and Mega Man III, and one Shadow Blade uses one unit in Mega Man 2: The Power Fighters. With a full energy gauge, it can be used 56 times in Mega Man 3, 38 times in Mega Man III, and 16 times in Mega Man 2: The Power Fighters.

Exploit
In the NES version of Mega Man 3, the player can use Shadow Blade endlessly by changing the weapon after each shot, avoiding a energy unit being used by the second Shadow Blade. This issue was fixed in later releases like Mega Man: The Wily Wars.

Bosses weak against Shadow Blade

 * Mega Man 3: Magnet Man, Spark Man, Doc Robot (Bubble Man and Heat Man), Kamegoro Maker
 * Mega Man III: Spark Man
 * Mega Man: The Wily Wars: Hyper Storm. H
 * Mega Man 2: The Power Fighters: Bubble Man, Wily Capsule

Bosses immune to Shadow Blade

 * Mega Man 3: Hard Man, Doc Robot (Air Man), Gamma (2nd phase)
 * Mega Man III: Punk, Wily Machine
 * Mega Man: The Wily Wars: Iron Ball, Wily Machine (Phase 2 and 3)

Other media
Mega Man uses the Shadow Blade against Kamegoro Maker in the cartoon Captain N: The Game Master.