Charmander- ground is the best IMO. Allows you to hit heatran ( unless you go mixed with earthquake lol).
Vivillon- I think fighting or ground, but fighting as the top one IMO.
Pansage- rock
Panpour-pretty sure it gets grass knot if I'm not mistaken, so fire I guess?
Pansear- ice or rock
Gothita- fire
Charizard gets Focus Blast for Heatran