These days, it seems like almost all of my best/favorite clothes are ones only appropriate to wear in the winter.
I suspect that this is partly due to a longstanding body image problem that has always flared up particularly badly in the summertime (like Regina Spektor says – summer in the city, it's “cleavage, cleavage, cleavage,” and heaven help you if you don't want strangers on the bus staring down/rating yours), and partly due to my love of wearing tights instead of pants, which I can generally only justify under sweater dresses.
...Well, I say generally. I am becoming steadily more shameless as I get older. At this point in time, for example, I have been seen publicly in sweatpants at least once. I like to think of it as half of the special secret shame shared between myself and the guy working the late shift at the 24-hour pharmacy. (The other half, of course, was the quart of Ben & Jerry's that I purchased and took home to consume by myself. You're welcome.)