Cape

It's the proportion and shape of that jacket that makes it special. It's cropped in a modern way, far above the hip and almost short-sleeved in the arms. It's also cut close to the body, but it's still swingy.

In all, the effect is one of insouciance, modernity, and sophisticated girlishness. (Never mind the fact that it's Sienna Miller wearing this Moschino capelet.)