Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Tunnelblick - free software for OpenVPN on OS X and macOS
Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
OpenVPN - OpenVPN - The Open Source VPN
Postman - The Collaboration Platform for API Development
WireGuard - Fast, Modern, Secure VPN Tunnel