You'll need to give us a lot more information before we can advise you. How experienced are you and your wife? Are you familiar with basic safety practices? What sort of play are you interested (pain, bondage, humiliation, just rough sex)?
Stick a needle through her clitoris. Then hook a wire up to the needle and another wire in her butt or tied around her toe. Electrocute her. Is that the sort of extreme you were looking for?
I have to agree with Smallest, WantSadist. That sort of advice is actually quite dangerous unless the person doing it is fairly skilled and experienced.