Even if you haven't heard of Anna Wintour, you've definitely read the magazine she is editor in chief of. Rumor has it that the character Miranda Priestly in the Devil Wears Prada is based on her. She has the job every fashionista dreams of and with her staple oversized sunglasses and blunt bob she's easy to dress as for halloween.
To complete the look a smug pout and crossed arms might help you get into character. To really go the extra mile, recruit a starbucks toting assistant to follow you around!