Gyarados is a pokemon from the original 150. His first form of Magikarp might suck, but he's one of the best water pokemon you can get. He's been one of my personal favorites for years.
I was really happy to receive him as a card. Not the rarest one you can find, but a proud moment in childhood.
Gyarados's original Japanese name ギャラドス (Gyaradosu) is pretty much the same. It's believed to be derived from 虐殺 (Gyakusatsu) which means "massacre" referring to Gyarados' violent nature in the game's summary.