Atahualpa is the theme to crown all themes.
It is amazingly easy for novices to use and the author has gone to a lot of trouble to document and teach, above and beyond the labours of building the code itself.
If you are new to customizing your web site Atahualpa gives you the whole world of WordPress to test and play with and in the process become ever more familiar with the entire platform. And with every dot release the author has been adding major new functionality. Version 3.4 gives the WordPress publisher the ability to easily customize or add external widgets all over a site, arbitrary links in the page navigation and a lot more.
This is the theme of which every non-programmer dreams. I can only imagine what a real programmer could do with Atahualpa as a starting point. The mind boggles.