This Carhartt is my favorite:

http://www.carhartt.com/webapp/wcs/store...tegoryId=10902#

If it gets cold, fold down the ear flaps (which also cover the back of your neck). If it gets really cold, fold down the face mask that is sewn/tucked inside.

The cap below is a close second. It's long enough that you can pull it way down so it covers the back of your neck.

http://www.carhartt.com/webapp/wcs/store...ategoryId=10902