15. The Lightweight Topcoat — Here is a list of all the reasons why you need one of these in your closet NOW: It's practical, it looks good on everyone, it's insanely chic, it goes from day to night, it's grown-up, it will make you look two inches taller, it works with jeans and dresses alike, and it's CHIC. Did we say that already? 

Roland Mouret Quilip Patterned Coat, $2,830, available at Net-a-Porter; Zara Crewneck Coat, $99.90, available at Zara.