Why it's on the list: Dips are a proven mass-builder on their own. Their only problem: Lots of people can't do enough reps to get within the ideal muscle-building rep range of 8-12 reps. Either that, or they can do way too many. In the former case, use the assisted dip/pull-up machine or a band. In the latter, add weight with a dip belt or a light dumbbell between your knees or feet.
Dips hit both the chest and triceps, but to favor the tris, keep your body as vertical as possible. Don't lean forward and keep those elbows tight to your sides. Think dips won't work for you? Take a look at any male gymnast; horseshoe triceps come standard issue with all those dips!
Dip Variations for Triceps Growth:
In your workout: You can start your triceps workout with dips if they're tough for you. Otherwise, use them in the middle of your workout to pump those arms full of blood. Shoot for 3-4 sets of 8-12 reps.