Steel is a decent choice as there aren't a drastic amount of Fire, Fighting or Ground Pokémon in HeartGold/SoulSilver, and you can use a Swords Dance / Extremespeed / Iron Head / Earthquake set which will do incredibly well.
If you've got a Special Arceus (as in it's SAtk is greater than it's Atk) then you can use a Dragon plate and go Calm Mind, Judgement (Dragon Pulse until Lv100), Thunderbolt and Ice Beam, or Flamethrower and Earth Power.