Magnetic Shockwave

Magnetic Shockwave (マグネティックショックウェーブ) is one of Onslaught's special moves in the game Marvel vs. Capcom: Clash of Super Heroes, which creates several shockwaves. Mega Man gains this attack in his ending from the game after defeating Onslaught, where he takes a Special Weapon Item and a get weapon screen with Mega Man 3's music shows him using the attack. Magnetic Shockwave can be used by Mega Man in battles in the PlayStation version of the game after completing the game with him.

Trivia
Magnetic Shockwave is the only weapon gained from a final boss (excluding the unnamed missile from Mega Man II's Wily Machine) and from a boss that isn't a machine.