Truly? Sex. After 29 years together, it's become a spiritual thing - I'm deeper in her mind than her body. We're also in perfect synch, we know each other's idiosyncrasies so well and which buttons to press.
If South Africa, Russia and Australia released the tonnes of diamonds they have stockpiled, the price would crash and De Beers would be valueless. Gold is rare, diamonds are common as muck.