I'll cut to the chase. I think a aggresive centipede would be awesome. A lawnmower in grass areas would be epic. A neutral stick bug would be sweet. Lastly an aggressive garden snake would be fantastic.
Centipede - Typically drier, flat, areas or underground. Hide could be used for better base upgrades like reinforced walls. The legs could be used for scimitars.
Stick Bug - Wandering around a lot of places, but mostly the giant tree. Legs can be used to make the rod of a fishing pole to catch tadpoles, etc.
Lawnmower - Leaves a trail of grass planks and either grass or dead gr