Wearing a trench coat always makes me feel so put together. It doesn't matter if you're just wearing a tee, jeans and sneakers underneath, you'll still look sharp.
My new favorite trench is this navy blue version from Tulle. They carry it at Therapy here in the Bay Area, so my friend Margaret hooked me up with her employee discount. It has a fantastic mod tulip lining inside. Size small fit me perfectly (usually a size 2).