vulhub/vulhub: Pre-Built Vulnerable Environments Based on Docker-Compose (github.com)
https://github.com/xct/xc - A small reverse shell for Linux & Windows
https://github.com/cytopia/pwncat - netcat on steroids with Firewall, IDS/IPS evasion, bind and reverse shell, self-injecting shell and port forwarding magic - and its fully scriptable with Python (PSE)
https://github.com/Kudaes/LOLBITS - C# reverse shell using Background Intelligent Transfer Service (BITS) as communication protocol and direct syscalls for EDR user-mode hooking evasion.