Pewter
In addition to its use for classic, rustic looking hardware pieces, pewter is the metal of choice for brands looking to add a bit of fun to their hardware collections. Anne at Home has the most examples of fun pewter knobs and pulls. Their pieces include a cow with a real working bell, a Southwest collection with guns and cowboy boots, an Ocean collection with animals and shells, and an Asian collection with Chinese characters. Since Anne at Home hardware is forged to order in America, they will make your pewter hardware in your choice of finish.
With pewter you'll be getting a substantial piece of hardware built to last.