If you're looking to target the deep-tissue muscle fibers, cable curls are a good bet. Since the pattern of movement is less stable with this movement, due to the constant tension provided by the cable, you will call all the stabilization muscles surrounding the biceps into play as you execute the exercise.
You can use a variety of different attachments to perform the cable curls including a rope, a straight bar, or rotating cable handles that allow you to work a single arm at a time.