An unstructured navy sport coat is like a good diver watch—a wardrobe workhorse that looks appropriate in any number of situations. Soft-shouldered and slightly relaxed, it exemplifies the current movement of "dressed down tailoring" that's defining the way stylish men want to dress these days. They're the kind of jackets that are ideal for the coming spring but make easy work out of layering when the weather's harsh. A blue blazer without the blue blood stuffiness, today's best versions are cut from a washed cotton, which gives your entire look a relaxed, rumpled elegance. A traveler's best friend, you can stuff it in a duffel bag and still arrive looking sharp. Best of all, it will only get better looking the more you wear it (as the fabric conforms to your body's natural shape). Which is good, considering the year-round use you could get out of a jacket like this.