These are the top FREE plugins for WordPress according to WordPress.com. This data is from September 2019.

• Akismet Anti-Spam – Used by millions of websites, Akismet filters out hundreds of millions of spam comments from the Web every day. Add Akismet to your site so you don’t have to worry about spam again.
• All in One SEO Pack – Use All in One SEO Pack to optimize your WordPress site for SEO. It’s easy and works out of the box for beginners, and has advanced features and an API for developers.
• All-in-One WP Migration – This plugin exports your WordPress website including the database, media files, plugins and themes with no technical knowledge required.
• Classic Editor – Classic Editor is an official plugin maintained by the WordPress team that restores the previous (“classic”) WordPress editor and the “Edit Post” screen. It makes it possible to use plugins that extend that screen, add old-style meta boxes, or otherwise depend on the previous editor.
• Contact Form by WPForms – Drag & Drop Form Builder for WordPress – WPForms allows you to create beautiful contact forms, feedback form, subscription forms, payment forms, and other types of forms for your site in minutes, not hours!
• Contact Form 7 – Contact Form 7 can manage multiple contact forms, plus you can customize the form and the mail contents flexibly with simple markup. The form supports Ajax-powered submitting, CAPTCHA, Akismet spam filtering and so on.
• Duplicate Post – This plugin allows users to clone posts of any type, or copy them to new drafts for further editing.
• Elementor Page Builder – A page builder that delivers high-end page designs and advanced capabilities.
• Google Analytics Dashboard for WP by ExactMetrics (formerly GADWP) – This Google Analytics for WordPress plugin enables you to track your site using the latest Google Analytics tracking code and allows you to view key Google Analytics stats in your WordPress install.
• Google Analytics Dashboard Plugin for WordPress by MonsterInsights – With over 2 million active installs, MonsterInsights is the most popular Google Analytics plugin for WordPress.
• Google XML Sitemaps – Use this plugin to greatly improve SEO to create special XML sitemaps which will help search engines like Google, Bing, Yahoo and Ask.com to better index your site.
• Jetpack by WordPress.com – Jetpack is a popular WordPress plugin created by Automattic, the people behind WordPress.com. The plugin brings many of the most powerful features available on WordPress.com to self-hosted WordPress sites and thereby contributing greatly to the improvement of WordPress powered blogs and websites.
• Really Simple SSL – Really Simple SSL automatically detects your settings and configures your website to run over https. To keep it lightweight, the options are kept to a minimum.
• TinyMCE Advanced – TinyMCE Advanced introduces a “Classic Paragraph” block for the block editor (Gutenberg). If you are not quite ready to switch to the block editor or have plugins that cannot be used there (yet), using the Classic Paragraph block is your best option. It lets you continue to use the familiar TinyMCE editor for most tasks, and at the same time gives you full access to all blocks and new features in the block editor.
• UpdraftPlus WordPress Backup Plugin – simplifies backups and restoration. It is the world’s highest-ranking and most popular scheduled backup plugin, with over two million currently-active installs. Backup your files and database backups into the cloud and restore with a single click!
• WooCommerce – With 80,876,475 downloads, WooCommerce is the most popular eCommerce platform for building an online store (stats from Builtwith).
• Wordfence Security – Firewall & Malware Scan – Wordfence includes an endpoint firewall and malware scanner that was built from the ground up to protect WordPress.
• WordPress Importer – The WordPress Importer will import the following content from a WordPress export file: Posts, pages and other custom post types, Comments, Custom fields and post meta, Categories, tags and terms from custom taxonomies, & Authors.
• WP Super Cache – This plugin generates static html files from your dynamic WordPress blog. After an html file is generated your webserver will serve that file instead of processing the comparatively heavier and more expensive WordPress PHP scripts.
• Yoast SEO – Yoast SEO is the most complete WordPress SEO plugin. It handles the technical optimization of your site & assists with optimizing your content.