The WYSIWYG module is my favorite for rich text editing in Drupal 6 and Drupal 7. (In Drupal 8, WYSIWYG is in core.) Here's how I set it up.

This module is essential for configuration management in Drupal 8

This Drupal 8 module allows to restrict text formats on fields.

From the Drupal module page, "The Metatag module allows you to automatically provide structured metadata, aka "meta tags", about a website."

This module, in a basic sense, allows the title to be an actual Drupal field. This comes in especially handy when doing translations, as titles are not translatable in core.

"Fieldgroup will, as the name implies, group fields together. All fieldable entities will have the possibility to add groups to wrap their fields together. Fieldgroup comes with default HTML wrappers like vertical tabs, horizontal tabs, accordions, fieldsets or div wrappers."

Download over 3.5 million times, this module is an insane query builder. Learn it.

The best reference module for Drupal. This is supposed to be in core for Drupal 8.

"The Media module provides an extensible framework for managing files and multimedia assets, regardless of whether they are hosted on your own site or a 3rd party site - it is commonly referred to as a 'file browser to the internet'.

Media is a drop-in replacement for the Drupal core upload field with a unified User Interface where editors and administrators can upload, manage, and reuse files and multimedia assets....

"File entity provides interfaces for managing files. It also extends the core file entity, allowing files to be fieldable, grouped into types, viewed (using display modes) and formatted using field formatters. File entity integrates with a number of modules, exposing files to Views, Entity API, Token and more."