While there are many themes available to server different purposes. There will always be something missing from the readily available theme. Customisation could be the answer but it is not recommended when there are enormous amount of changes to be made.
The answer to the above issue would be to create your own proprietary theme from scratch. There are many ways to get started create a theme from base.
1. Create a theme from Wireframes, then design, then HTML and finally the WordPress theme.
2. Create a theme based on another website.
3. Create a theme from existing HTML.
4. Create a design from PSD files.
Whatever your requirement, give me a shout and we can take it further.