The deltoids. Your shoulder muscles. They're small and often overlooked, but they're impactful. Just look at some of Hollywood's leading men—they don't have to be stacked, but almost all of them have decently developed delts. That's because working your shoulders broadens out your frame, which visually slims your waist and carves out that coveted V-shape. And since you've likely never properly pushed your shoulders like this, you'll notice muscle gains much quicker than anywhere else on your body.