Consider This: Hugh & Crye L'Enfant Blazer in Navy Hopsack, $245

A suit jacket is too structured to ever look fully casual. When you want to take your kit up a few levels without going all-out, opt for an unstructured blazer. This lightweight, slim version from Hugh & Crye comes in twelve different fits based on a variety of body types, so for many guys it's the closest thing to made-to-measure. If you only get one—get navy. Then throw it on before a date, or just a night out, it's an instant style upgrade that'll set you apart from the herbs.