We are one of the first Drupal teams in the world who have successfully built a Drupal 8 Portal using Headless Drupal technique. Here Drupal 8 is used to develop the back-end and Angular.js to build the front-end. Some of the cool features of the site are carousel for latest news (Carousel module is still not stable in D8 but using JS one can create carousel), category wise news, sub-menus and persistent header.
View Headless Drupal Demo