Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
tcpdump - tcpdump is a common packet analyzer that runs under the command line.
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.
Postman - The Collaboration Platform for API Development
Ettercap - Ettercap is a suite for man in the middle attacks on LAN.
Proxyman.io - Proxyman is a high-performance macOS app, which enables developers to view HTTP/HTTPS requests from apps and domains.