Who is your ace Pokémon in HeartGold/SoulSilver?

Mine is Houndoom. I've loved that Pokémon ever since its debut in "Houndoom's Special Delivery". It's also the best cause the Egg you receive from Professor Elm hatches into a Togepi (it evolved) and to me, they're perfect for double battles. I have a pic but it says this community doesn’t allow images.

What about you? Which Pokémon would you consider your ace?