A typical black-tie number is floor-length, unless it's got intricate embellishments that dazzle or a killer statement sleeve that looks as though it belongs on the red carpet. A superformal gown is the most fun to shop for — you should keep your power color and best assets in mind and choose a piece that's memorable. You'll be posing for photos, after all, and absolutely everyone will be dressed to impress.
Nothing screams more formal than this beautiful Zac Posen gown ($790).