Neck muscles keep your spine aligned and protect the region from high-impact situations such as a football tackle or a whiplash injury from a car accident. Men strive for large neck muscles because it gives a strong and athletic appearance similar to professional athletes. There is equipment designed specifically to train your neck; some of them you'll find at the local gym, while others are more common in sports performance centers.
The neck harness is arguably the best of all neck-building equipment. You place the harness on your head like a helmet and drape the chain over your chest where you attach weight plates. You crouch down and allow the chain to dangle in the air. Repetitions are completed by alternately looking straight ahead and then looking down so your face is parallel with the floor. You can change the angle of the pull by tilting your head left or right and completing the reps that way. This ensures that your entire neck is worked.
A lot of the equipment useful for neck exercises can be useful for other parts of the body as well. Cable shrugs or upright rows can be completed by attaching a straight bar to the pulley. Two cables can be used at once to complete shoulder presses -- a deltoid exercise that also works the neck. If you're combining neck days with other body parts, the cable machine can quickly be adjusted for biceps curls, lat pulldowns, oblique rotations, cable crunches and more.
Free weights are similar to cable machines because they are all-in-one equipment. The difference is that you are not lifting weight with the aid of a pulley, which makes balancing the weight a little harder. Dumbbells, weight plates, barbells, kettlebells and medicine balls can be used to complete deadlifts, presses, upright rows or kettlebell swings and will dramatically increase the size and strength of your neck. Try the fireman's carry: Find an open space in which to walk, grab two dumbbells and hold them at your sides. Walk in a large circle for 30 seconds, then set the dumbbells down.
The flat bench is used in combination with free weights. Performing exercises sitting down forces your upper body to keep still, ensuring that the shrugs and presses you perform will work your neck harder. The "plate neck resistance" exercise must be performed on a bench for proper range of motion. Lie flat on a bench face up with your neck hanging over the end of the bench -- your neck should be parallel with the bench starting off -- and plant your feet on the floor. Hold a weight plate a few inches away from your forehead, then dip your neck back in a semicircular motion; repeat to return to the start.