It would be hard to pinpoint one meal, but those that stick in my memory, are on a beachside cafe many years ago, Pampelonne Beach in France, an Omelette Aux Fines Herbes, didn't have much money at the time, but a finer omelette I have yet to taste!
A Chinese boss when I worked at a firm of chartered accountants took some of us out to a Chinese restaurant only known to him and ordered for us, I particularly remember it was best Chinese food I had ever tasted, steamed whole Sea Bass with Soy and Ginger will forever etched in my memory as overwhelmingly delicious. Can't remember the actual restaurant. 
A birthday meal in the much lauded River Cafe in London met all expectations.
My 60th birthday meal in Hotel des Cataratas, Iguazu, Brazil, best hotel I've ever stayed in, fabulous food even the breakfasts were sensational.