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.
Surge for Mac - Advanced Web Debugging Proxy for Mac & iOS
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
Weer - A HTTP protocol debugger with Chrome DevTools frontend interface
Ettercap - Ettercap is a suite for man in the middle attacks on LAN.
Cellist - Cellist is an all-in-one HTTP debugging proxy software designed for OS that provides a straightforward approach to put a proxy between the HTTP client and the internet.