Let's say I'm a Western Europe traveler... :p Been to Portugal, Spain, France, Italy, Belgium, Luxembourg, and Germany. Favorite countries it's hard to say, but some of my favorite cities I've been to are Vilamoura (Portugal), Paris (France), Aachen (Germany), and Naples (Italy).
My number 1 dream destination would definitely be the USA. I'm a big admirer of American culture and history, and the whole country sounds magnificent but I'm particularly attracted by the big cities. I'd love to live in a city full of skyscrapers. Plus, as a future programmer, the career prospects are better in the US than anywhere else in the world so it's one of my goals to move there as soon as I can.
Australia is a close second. It also has the whole package: big cities, beaches, wide-open spaces, etc. And in terms of weather it sounds like paradise.
And then I'd also love to visit the UK, the Scandinavian countries (not to live there, though, way too cold for me... :p), and a number of tropical islands/archipelagos such as the Bahamas, the Maldives, and Bora Bora.