The Wife loves nipple play, clamping on nipple clamps not only makes her nipples rock hard but also sends shockwaves to her pussy (her words not mine!).
She has contemplated getting her nipples pierced to see if it has the same affect as the clamps but she loves the process of slowly putting the cold, hard, metal clamps on and tightening them up a turn at a time until the pain is absolutely adorable. Then I love putting them in my mouth and flicking the nipple with my tongue and tugging them gently. Heaven.
She may get them pierced one day but for now these are rocking her world.