The Pro-Key is a superb nut key with a host of great features (including a leash) to help recover stuck gear.
The Pro-key comes with a new precision ground tip which allows access to the smallest slots, as well as a wire gate at the top which allows a direct clip to the harness. Added to this, a one piece 'folded top' gives a bigger surface area to allow a strong push with the palm. Large holes keep the weight down.
Finally, and exclusively, the Pro-Key Leash comes with an extendable detachable and flexible leash which can be clipped (via a mini-wiregate biner) to your harness preventing loss in extreme positions.