For me the first place would be any of the countries bordering Iguazu Falls in South America - maybe Argentina. Since I live in Italy and have a home in Colorado in the US, I've already seen a lot of Europe, North America and the Caribbean, but have never been to South America although I've been close enough to see the coast of Venezuela. I particularly like waterfalls and Iguazu looks spectacular. http://www.iguazuargentina.com/
Machu Picchu
hmm so many
Thailand
Hawaii
Eastern Islands [[really any small tropical island]]
Japan
Wales
South Africa
Costa Rica [[went before but want to go to the rainforest this time]]
Japan! It's absolutely a beautiful place and their culture is really cool.. they have amazing buildings built out of clay!
If you are planning for thailand , malaysia , indonesia then include maldives also in your list , its a beautiful unexplored travel destination.
I would love to see Ireland cus my family is very irish and it would be cool to see where my family came from.
The grand canyon, always see it in pictures, but i would like to take my whole family there.