I like the idea of having a dog (being a dog owner may play a part in this). It gets lonely out in them woods, a companion to make a bond with plays into the psychology of the game well I think. Also not forgetting the realistic element - people have dogs, fact. It's not like it's a robot or a summoned demon familiar. Could a dog be used for hunting small animals maybe? or tracking, if you cross an area that has recently been walked on by another human, the dog could signal and lead you? then you'd have a choice to follow someone, or even use it to set a trap for someone you think has a dog and is following you?