DevKinsta

DevKinsta

Design, develop, and deploy WordPress sites from the comfort of your local machine.

A Free local WordPress development suite by Kinsta. Available for MAC and PC, it offers lots of convenience such as one-click site creation, database management, HTTPS, email testing and, error logging.
kinsta.com/devkinsta
Ray

Ray

Advanced dump Debugging tool for PHP

Ray is a lightweight desktop app that helps you debug your PHP app. You can get a free demo that can be unlocked with a license. You can use Ray in WordPress by manually cloning the repo or installing the plugin via the Plugins section on the WordPress admin UI.
myray.app
Responsively

Responsively

A must-have DevTool for all web developers that will make your job easier.

Responsively is An open source tool that lets you inspect a web page on multiple screens. It comes with several very handy features such as the ability to inspect elements, a list of common devices screen size, coaching control, and more.
responsively.app
Local

Local

A fuss-free way to develop WordPress locally

Local by Flywheel is THE BEST  way to set up a local wp installation. Very simple to use with lots of handy features.
localwp.com
The WordPress Plugin Boilerplate

The WordPress Plugin Boilerplate

A standardized, organized, object-oriented foundation for building high-quality WordPress plugins.

Laying the foundation so that you can get to work on building your next big thing.
wppb.io
JS Operator Lookup

JS Operator Lookup

This nifty little project lets you type in or select a JavaScript operator, and it tells you about it!

By Joshua Comeau of www.joshwcomeau.com joshwcomeau.com. Joshua built this project because he was sick of forgetting what these blasted operators are called. Often he'll remember the operator's syntax, but not exactly how it works. One can't use search engines to find out more about them, since they ignore "special characters"!
Operator Lookup