Elementor - Elementor is a front-end drag & drop page builder for WordPress.
Themify Flow - Drag & drop Wordpress theme builder
Pinegrow WP - Convert static HTML websites to WordPress themes.
Layers - A simple Wordpress site builder & its free forever
Divi Theme - A flexible WordPress theme with the power of Divi Builder built in.
Bulma - Bulma is an open source CSS framework based on Flexbox and built with Sass. It's 100% responsive, fully modular, and available for free.