Aquamentus was the first boss to ever appear in the Zelda series. He serves as the threat at the end of the first dungeon. One of my favorite boss battles in the series.
Even though his NES form is a little wimpy today, back then he was force to be reckoned with. Well at least to my 5 year old self.
He made a return appearance in Oracle of Ages, sadly though I never had a chance to play that game.
He also had a cameo in that awful cartoon series.