An easy-to-use reference cheat sheet for just about any programing language known to men.

AskJarvis is a development assistant that helps you code faster with syntax and documentation generators, a codebase, IDE extensions, and more.

codinDevtoys is a very handy collection of tools for your daily dev grind. Lots of useful sections like Regex Tester, Markdown Preview, Image compressor, JSON Formatter, and more. It is Free, open-source, and offline!

A user-contributed mega list of cool WP development tools.

The WPScan WordPress Vulnerability Database is a database of WordPress vulnerabilities, plugin vulnerabilities, and theme vulnerabilities. You can install the WPScan WordPress Security Plugin and Start Securing Your Website.

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.

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.

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.

Local by Flywheel is THE BEST  way to set up a local wp installation. Very simple to use with lots of handy features.

A Q&A tool for finding answers to your coding questions. Comes also as a site you can browse in, or a handy chrome extension.