Yoast - Yoast offers plugins to improve SEO and optimize web sites and blogs.
WP Rocket - WP Rocket offers a caching plugin for Wordpress.
Wordfence - Comprehensive security plugin for WordPress.
Autoptimize - Autoptimize makes optimizing your site really easy.
Jackmail - A newsletter plugin for Wordpress.
WP Super Cache - A very fast caching system for WordPress that produces static HTML files.