I've wanted Gyarados to be Water/Dragon. It makes more sense, and it's an amazing type. True, he has a useful Flying immunity, but half the time he's felled by Electric and Rock moves.
Except it doesn't actually make more sense. I'm pretty sure Magikarp->Gyarados is based on the Chinese myth of the Dragon's Gate. A carp climbed the river to the gate and was able to jump over it, becoming a dragon. However, he abused his new power as a dragon, so his dragon status was taken from him.
"Power of mind is infinite, while brawn is limited." Koichi Tohei Official Chespin of the Pokemon X board.