Yamato Spear

Yamato Spear (ヤマトスピア) is Yamato Man's Special Weapon. It allows Mega Man to fire small spearheads forward at a high speed. When rapid-firing, they make a v-shape.

Robot Master and Bosses Weak Against Yamato Spear

 * Knight Man: Mega Man 6
 * Mechazaurus: Mega Man 6

Triva
It should be noted that this is the only weapon that can sneak past Knight Man's shield.