Of places I haven't been to yet, I would opt for Thailand, Burma, Indonesia, Malaysia. Also Singapore. And any tropical island with a beautiful beach: Maldives, Seychelles, Mauritius
Asia is definitely my first choice.
I'll also determined to go to Australia some time in the next few years, and maybe New Zealand.
In South America: Chile, Argentina
In Africa: Marocco, South Africa and Kenya.
In Europe: Portugal, Italy and Sweden.
There are just to many fascinating places in the world; I want to see them all!