Mine would have to be Japan. I've only got to go once so far, but from start to finish the trip was a blast. Even the trip to Hiroshima. And for a vacation where I almost wound up in the pokey I had more fun than I most other of my vacations combined.
Hong Kong. Besides, the stuffy air and the bad traffic, the place is just awesome. You can literally buy anything there. It's pretty good for manga lovers too. I found a lot of anime figures for pretty cheap. There are lots for technology lovers too. Brand new shit that hasn't come out in North America yet. Food, malls and a ton of other stuff.