Rain Flush

Rain Flush (レインフラッシュ) is Toad Man's special weapon. This creates an acid rain storm that affects all things on the screen (provided they are vulnerable to it), and can hit several times before disappearing. In Mega Man IV, it can extinguish the fire in Napalm Man's stage for a short time.

Capacity
Rain Flush uses 4 weapon energy units in Mega Man 4 and 1 unit in Mega Man IV. With a full weapon energy gauge, it can be used 7 times in Mega Man 4 and 19 times in Mega Man IV.

Bosses weak against Rain Flush

 * Bright Man: Mega Man 4 and Mega Man IV
 * Charge Man: Mega Man IV
 * Wily Machine: Mega Man for the Sega Game Gear

Other media
Mega Man uses the Rain Flush in episode 10 of Ruby-Spears' Mega Man animated series.

Trivia

 * The Rain Flush can be used as a substitute against Pharaoh Man if one has run out of Flash Stopper, though you'll have to contend with Pharaoh Man's speed.
 * If Rain Flush is used on Wily as he escapes the first battle on Mega Man 4, he will be destroyed, but as a result you will be stuck on the stage unless you reset.