The Get RX'd Light Bulb adds a whole new grip element to your pull ups. 

Additionally, the Light Bulbs can be put in a number of different sequences to give you a challenging Light Bulb Grip obstacle course:
Add them along the square crossbar of your rig, and you have a miniature obstacle course you must move across sideways. Add them along the upright of your rig, and you have the ability to climb up and down.