Whether you're attending your best friend's wedding, or getting ready to take a brisk walk with your favorite canine, there's always a reason to wear a vest jacket. A sleeveless design that will slip on over shirts, T-shirts and sweaters, a vest jacket by Saks Fifth Avenue and ASOS will look great with tailored pieces. For warmers styles, you can't go wrong with a vest jacket by DSquared² and Helmut Lang.