Black Wave

Black Wave is the Special Weapon used by the Roboticized Master Rouge Woman in the crossover Worlds Collide. Mega Man's colors when using this weapon are white and black with pink trim.

Reportedly a stun gun, this weapon's effects have not been directly observed in the comic, although Rouge Woman briefly fired it at Knuckles the Echidna and Shadow the Hedgehog during the battle of the Robot Masters. The blasts are purple in color, leave rings of displaced energy in their wake, and appear to be similar in size to Mega Man's usual charged shots.

Trivia

 * Mega Man himself did not fire the weapon on-panel once, although given the lateness of its acquiring it can be deduced that it may have been the weakness of Wily Egg guardians such as the Chaos Devil, the Egg-Wily Machine X, or both, following the pattern of classic Mega Man games.
 * According to Ian Flynn, if he got the chance to combine Metal Sonic and Bass, the combined entity's weakness would've been this weapon. (Source?)