Skullmet

Skulmet is an enemy in Mega Man 4. On one side it looks like a skull and the other side has a one eye. To destroy it Mega Man must shoot it in the eye (charged shot is best). The Rain Flush attack will destroy it in several hits despite where Mega Man is standing as long as they're on the same screen.

Trivia
It's name "Skullmet" may be a reference to the classical enemy Met.