Water/dragon type. That's a powerful combination. Only another dragon type would have more than 1x effectiveness against it (in this case only 2x so it's not double weakness). Considering that other dragon types are rare, and that they themselves would be weak to the dragon moves that I have, it'd balance out. Reminds me of Dragonite. Water origins, only keeping up with the water. It'd be a nice type combo.
Definitely be either fighting Pokemon. If they had fighting starter Pokemon I would probably choose them almost every time (Which would explain why I love Blaziken and Infernape). I don't really know why I like the fighting type Pokemon, though my final team in Red/Blue/Yellow always has a Primeape, and my final team for Crystal will probably have a Hitmontop or Hitmonchan.