Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.
gitsome - Supercharged Git/Shell autocompleter w/ GitHub integration
Endpoints - View and respond to requests on an HTTP endpoint
Kite - Kite helps you write code faster by bringing the web's programming knowledge into your editor.
httpbin(1) - HTTP request and response service
YOURLS - YOURLS is a website that contains all the tools you need to create and launch your very own URL shortener. URL shorteners like bitly or TinyURL are fine for public use, but they offer limited options in terms of URL customization.