Sublist3r - Sublist3r is a python tool designed to enumerate subdomains of websites using OSINT.
Shodan - Shodan is the world's first search engine for Internet-connected devices.
SpiderFoot - Open source intelligence (OSINT) automation tool.
Censys - Censys helps organizations, individuals, and researchers find and monitor every server on the Internet to reduce exposure and improve security.
sn0int - sn0int is a semi-automatic OSINT framework and package manager
Exploit Pack - Exploit Pack is an open source project security that will help you adapt exploit codes on-the-fly.