A wool peacoat is the coat I would buy first if I owned only one. The Toteme wool and cashmere-blend version leads this edit, and the Isabel Marant belted herringbone coat is the one with more personality. Further down are long double-breasted styles from The Row and L'Agence, plus faux fur and puffer options for the coldest days. Get the weight right and it works for years.

 

For the classic shape on its own, there is Peacoats, and for the puffer side, Cropped Puffers.