With about a month of summer left, it's about time to start pulling out your knitwear. This cluster of must-have men's sweaters is full of cool cardigans, v-necks and vests. Those who prefer a preppy East Coast cool look may throw on a polo or a bow tie on under a v-neck sweater. While you hipsters may rock a skinny tie with cardigan and some selvage denim. Regardless of how you wear them, everyone needs to check out these must-have men's sweaters.