real-world examples of progressive web apps

What websites, visited by millions of users on a daily basis, have mobile-like counterparts, “turbocharged” with powerful native apps-specific features? In other words, what are some of the most famous real-world examples of progressive web apps? For, there's no better way of convincing yourself that PWAs are (far) more than just a buzzword, than by witnessing big names rushing to invest in this “trend”, right? Well, I've done my research and hand-picked 3 of the highest trafficked progressive web apps for you to... get inspired.