Product shapes are capable of trademark protection under the rapidly expanding doctrine of trade dress.  As long as the product shape meets the requirements under trademark law of distinctiveness, andunobjectionable content, and the shape is not a functional feature of the underlying product, it qualifies for trademark protection, and can be registered with the US Trademark Office.

Examples include the famous Coca-Cola bottle, 

and the fish-like shape of a Pepperidge Farm cracker.