What's the best move you've ever seen?

On my QF6 (that's not Queen to f6! ) flight from Singapore to Sydney this morning, I could not get any sleep and had to switch on my pocket pc to review some great endgame compositions. I then found the following beauty. What would you play here as white and, more importantly, why?

btw, either Airfrance or Qantas have managed to lose my suitcase. I only have a pair of trousers and a shirt to wear now...