In Gen 6? That would be Blastoise, especially if you have the mega option.
Scald and Rapid Spin and Roar are important. Avalanche is good, because you will be investing no points in ATK or SP. ATK, so having one solid SP. ATK, Scald, and one Solid ATK, Avalanche gives you some key strats. Also, Blasty's abysmal speed means the Avalanche -4 priority is not a problem at all, so it creates a nice 120 BP Ice Phusical Attack.
Rapid Spin aids your team against counter set ups. Roar helps Blasty stop an opponent from setting up on him AND gets through temp invulnerable situations such as Substitute and Protect.