THEMING

Advanced Custom Fields
This plugin enables the easy creation of additional fields that can be attached to any content type …
https://wordpress.org/plugins/advanced-custom-fields/

ACF – image aspect ratio crop
when you can’t trust the images to be correctly prepared
https://wordpress.org/plugins/acf-image-aspect-ratio-crop/

DEVELOPMENT

Backup Buddy
This is a paid plugin, but well worth the cost. Facilitates easy backups and transfers
https://ithemes.com/purchase/backupbuddy/

Duplicator
A “free” version of Backup Buddy that works in a very similar fashion …
https://wordpress.org/plugins/duplicator/

Regenerate Thumbnails
Cope with changed or new image sizes after the fact
https://wordpress.org/plugins/regenerate-thumbnails/

WP-Optimize
caches your site, cleans your database, compresses your images.
https://wordpress.org/plugins/wp-optimize/

User Role Editor
Extends the 5 default WordPress user roles and allows control over most privileges by role…
https://wordpress.org/plugins/user-role-editor/

PublishPress Capabilities
manage user level access & privilege
https://wordpress.org/plugins/capability-manager-enhanced/

WordPress DB Pro
Syncs one database with another …
https://deliciousbrains.com/wp-migrate-db-pro/

What the File
shows the active template file
https://wordpress.org/plugins/what-the-file/

Plugin Detective
helps troubleshoot site errors
https://wordpress.org/plugins/plugin-detective/

Theme Check
checks for standards compliance
https://wordpress.org/plugins/theme-check/

PHP Compatibility Checker
checks site for PHP version compatibility
https://wordpress.org/plugins/php-compatibility-checker/

FORMS

Gravity Forms
This is a paid plugin… very sophisticated form construction, storage of responses, interaction with payment gateways …
http://www.gravityforms.com/

Ninja Forms
An old reliable that will handle most common needs!
https://wordpress.org/plugins/ninja-forms/

SEO

Yoast SEO
Gives you the metatag control that core WordPress doesn’t … and dynamically generated sitemaps!
https://wordpress.org/plugins/wordpress-seo/

MonsterInsights
connecting with analytics the easy way
https://wordpress.org/plugins/google-analytics-for-wordpress/

ACF Content Analysis for Yoast
improves index visibility for custom fields
https://wordpress.org/plugins/acf-content-analysis-for-yoast-seo/

Schema
for adding schema.org structured data markup
https://wordpress.org/plugins/schema/

MENU ENHANCEMENT

If Menu
Allows you to set conditions to a menu item visibility
https://wordpress.org/plugins/if-menu/

Menu Image
insert icons into classic menus
https://wordpress.org/plugins/menu-image/

Mobile Menu
responsive menu for classic menus
https://wordpress.org/plugins/mobile-menu/

MAPS

RVM – Responsive Vector Maps
Need a linked vector map?
https://wordpress.org/plugins/responsive-vector-maps/

Store Locator
interactive maps
https://wordpress.org/plugins/agile-store-locator/

SLIDER

Smart Slider 3
flexible, lightweight and free
https://wordpress.org/plugins/smart-slider-3/

EVENTS

The Events Calendar
The “free” version is packed with features, and the paid version makes it even better
https://wordpress.org/plugins/the-events-calendar/

COMMERCE

Woo Commerce
The WordPress e-commerce solution … the “free” version allows quite a bit and the add-ons do everything else
https://wordpress.org/plugins/woocommerce/

LEGACY STYLE

Classic Editor
when you don’t want to use Gutenberg
https://wordpress.org/plugins/classic-editor/

Classic Widgets
when you can’t let go of the old style of widgets
https://wordpress.org/plugins/classic-widgets/

PERFORMANCE

WP Rocket
superior caching plugin
https://wp-rocket.me/

Simple History
tracks login & user activity
https://wordpress.org/plugins/simple-history/

Redirection
crucial for coping with old URLs
https://wordpress.org/plugins/redirection/

SPECIALTY

Radio Buttons for Taxonomies
when you only want to allow a single choice
https://wordpress.org/plugins/radio-buttons-for-taxonomies/

FacetWP
for that Amazon like filtering menu effect
https://facetwp.com/

SECURITY

Disable XML-RPC-API
disable XML-RPC API and Pingbacks,Trackbacks
https://wordpress.org/plugins/disable-xml-rpc-api/

Limit Login Attempts
helps against brute force login attacks
https://wordpress.org/plugins/limit-login-attempts-reloaded/