Hard to decide. The Serpentine Spy is awesome because it allows me to play Plado Emberstorm with Kobold Miner, Elven Cutthroat, Serpentine Spy and Enchanted Pixie/Beetle Queen for the Inspire ability. Such a fast beatdown deck!

But War Chaang is beyond awesome. Just look at what it can do:
https://splinterlands.io/?p=battle&id=756cb85849fc6708a8ee426334a58f5df7132a06