Dog Pond - Place a plastic kiddie pool in the ground. It'd be easy to clean and looks nicer than having it above ground. Big dogs can't chew it up or drag it around. Then in winter months turn it in to a fire pit!
Old wooden barrel can be used as pet house to accommodate your dog or cat in garden. Barrel would nicely blend in the garden. However you need some support work for the barrel to stay where you put it and not to roll away