Grid Layout & Layout Builder
I've been working on a personal site that I've maintained since before I even got involved with Drupal. It's been iteratively migrated and upgraded from those early days on pmachine to its current iteration on Drupal 7. Obviously, I've been planning to upgrade it to the newest Drupal 8. All in all, this has gone pretty well, but as a big contributor to Layout Builder, I really wanted to use it on the site as much as possible. This hasn't gone anywhere close to how I would have liked. :-(