Modules

Nearly Every Site

Module Project Page Notes
Admin Toolbar https://www.drupal.org/project/admin_toolbar
Gin Toolbar https://www.drupal.org/project/gin_toolbar
Pathauto https://www.drupal.org/project/pathauto
Token https://www.drupal.org/project/token

Would Use Again

Module Project Page Notes
Better Exposed Filters https://www.drupal.org/project/better_exposed_filters
Config Pages https://www.drupal.org/project/config_pages Context handling is weird and documentation is sparse, but handy for quickly setting up configuration pages for things that can live in the database.
Corresponding Entity References https://www.drupal.org/project/cer/ Beta release, not covered by security policy.
Chaos Tool Suite (ctools) https://www.drupal.org/project/ctools/ Is a requirement of so many modules it typically gets installed as a dependancy.
Extra Field https://www.drupal.org/project/extra_field/
Group https://www.drupal.org/project/group/
H5P https://www.drupal.org/project/h5p/ Drupal integration of https://h5p.org/
Linkit https://www.drupal.org/project/linkit/ Adds an autocomplete field to the CKEditor Link button widget. Can enter links using node title. Can also be configured to add links to Media entities.
Profile https://www.drupal.org/project/profile/
Twig Tweak https://www.drupal.org/project/twig_tweak/
Views Bulk Operations (VBO) https://www.drupal.org/project/views_bulk_operations/

Development

Module Project Page Notes
Devel https://www.drupal.org/project/devel/
Examples for Developers https://www.drupal.org/project/examples
Twig Tweak https://www.drupal.org/project/twig_tweak/
WebProfiler https://www.drupal.org/project/webprofiler/

Curious About

Module Project Page Notes
Default Content https://www.drupal.org/project/default_content
Devel Kint Extras https://www.drupal.org/project/devel_kint_extras There seem to be a couple of ways of using Kint. Haven’t tried this one. Article: How to Print Variables using Devel and Kint in Drupal
Hux https://www.drupal.org/project/hux Allows hook implementation as module plugin. Info post: A modern alternative to Hooks
In Other Words https://www.drupal.org/project/inotherwords Provides field formatters for presenting lists of items in a more grammatical way and for condensing sequential lists into shorter text.
Schema.org Blueprints https://www.drupal.org/project/schemadotorg Nice YouTube overview: Schema.org Blueprints in 7 minutes
Structure Sync https://www.drupal.org/project/structure_sync
Taxonomy Views Integrator https://www.drupal.org/project/tvi Article: How to Customize Taxonomy Terms Pages?