Dragonite. Since its in the original 151.
I just love Dragonite's design and its overpowered attack. I practically owned every once I had a Dragonite in my gold game. (those were the days)
I will also put my least favourite psedo-legendary. Its Metagross, I find it gross Just not a fan of many 3rd Gen Pokemon designs and Metagross is one of them. Salamance's is quite okay.