My favorite theming modules for Drupal 8

theming modules for Drupal 8

The field formatter class module is a fantastic contributed module for custom theming Drupal 8 fields. It allows you to add classes to the outer HTML wrapper for any field display, so that CSS and Javascript can target them.

I find this particularly useful to theme different content type nodes using the same field types. https://www.drupal.org/project/field_formatter_class