"The Lair of Putzuputzu" by Gabriel Pickard and Alex Morgan
One thing I love about this OPD is that it is an elaborate and deadly game of mini-golf (or put-put golf depending on where you live). I didn't realize this at first, but by the end I was having a full on "Keyser Soze" moment. Lord Mulligan/ the narrow gap through the gate/the water trap/ tunnels in the cliff/ the windmill/
Putzuputzu! Damn it Pickard and Morgan! You guys made me feel pretty stupid when I realized how long it took me to grasp the hook of this OPD. Oh well. It is clever.