Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
Debookee - Debookee is the simplest & most powerful network traffic analyzer for macOS.
HTTP Toolkit - Beautiful, cross-platform & open-source tools to debug, test & build with HTTP(S). One-click setup for browsers, servers, Android, CLI tools, scripts and more.
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.
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface
Ettercap - Ettercap is a suite for man in the middle attacks on LAN.