Mega Man 4/Toad Man

Toad Man's stage is filled with areas in which a heavy rain is falling constantly. When you jump, this rain will push you backwards, so be prepared to compensate for this, each time you have to jump. If you're not careful, the rains will carry you to a premature death.

Twice in the stage, you'll encounter a toad-like mini-boss. This boss has two ways of attacking - firing explosives out of its back, and launching its eyes off of its body toward our hero. Dodge these attacks, and fire at the robot's eyes when they open.

Eventually you'll reach Toad Man. And all I can say is, this guy is a joke. Technincally, his weakness is the Drill Boomerang, but even if you got it by defeating Drill Man first, don't bother using it. Use your regular weapon, and rapid fire the guy. He'll jump over your head. When he lands, rapid fire some more. He'll repeat this strategy for the entire battle, NEVER FIGHTING BACK. Just keep rapid firing, and he won't get a chance to unleash his Rain Flush attack. Arguably the easiest Robot Master of all time. An easy victory.

Victory here gets you the Rush Marine, useful in underwater areas.