Giant Skeleton Things
These skeletons are large, and in addition display at least one feature that makes obvious their non-human origin (e.g., tusks, or small curved horns, or a tail). They possess some degree of sentience, as they speak, albeit only in a guttural alien tongue. Some possess huge weapons, but others prefer to attack by hurling pieces of their own skeleton (e.g. ulnae, femurs) as missiles (those bones regenerate somehow).