There are a few top quality theme developers that use Hammer to design their themes, before distributing the, via the popular (albeit somewhat controversial among some corners of the development community) marketplace Themeforest.
Here are some of the developers & designers that I've come across so far
WeAreKillr Themes - Themeforest
Bootstrap Guru - Themeforest
Pinsupreme.com - Themeforest
Please let me know if there are any more, I'd love to hear...