A trainer offers a different approach:
The Special Weapons (Metal Blade, Thunder Beam, etc.) are fun, but running out of ammo forces you back to the Mega Buster. A trainer can provide or a Weapon Selector that lets you switch to any boss weapon on the fly. mega man legacy collection trainer
Added to the first collection (Mega Man 1-6), this lets you hold a button to scrub backward in time and undo a missed jump or a hit from an enemy. Database & Boss Practice: A trainer offers a different approach: The Special