Attention: the Piquin or pequin (pee-KIN) is one hot chile!
Native to the American Southwest it was, likely, an original chili con carne ingredient. Take precautions to avoid inhaling powder or contacting sensitive areas.
Chile piquin has it's own slightly smoky flavour even though it isn't a smoke dried chile. This and a slightly citrusy accent make it a favourite in many Mexican dishes.