Yoast - Yoast offers plugins to improve SEO and optimize web sites and blogs.
Carbon Fields - Carbon Fields makes it easy for you to create custom fields for post types, taxonomies,
Jackmail - A newsletter plugin for Wordpress.
Pods Framework - Plugin and framework for adding custom fields and custom content types to WordPress.
Wordfence - Comprehensive security plugin for WordPress.
WPforms - Drag & drop WordPress form builder