Duck hearts... Only time I've had them is at one of those Rodizio places. Any of you guys been? It's basically a South American BBQ place. You get a card that's green on one side and red on the other - you leave it facing green and they keep coming round with a skewer with various meats (Duck hears being one) and carve it onto your plate. They only stop bringing you meat when you flip your card to red (there's also usually a good quality buffet with salad, nice lasagne, pinto beans, fried potatoes, rice etc etc.)
It's deliciously fatty and salty, which also keeps you drinking like a maniac . Last time I went I was stoned. Furthermore, I can't stop myself trying to get 'my money's worth' [you can take the man out of yorkshire...] so was basically eating meat non stop for 2hrs +, plus drinking gallons of stella.
It was the only time I've nearly been sick on a table, Mr Creosote style. I managed to shuffle, very slowly, to the exit, after settling the bill, and managed to reach a bin in the o2 centre in the nick of time. Gastronomy at its best!