Ask HN: What are your favorite examples of being surprised/delighted by UX?

Some web and mobile apps take UX to the next level by introducing fun and surprising elements to the experience. Things that have no functional impact but that make the product come alive and have personality. For example Yelp's mobile app refresh: https://cdn-images-1.medium.com/max/1600/1*hAEq-oz-z4VmtUw1j6eIuA.gif