OWASP Amass - An advanced open source tool to help information security professionals perform network mapping of attack surfaces and external asset discovery using open source information gathering and active reconnaissance techniques!
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.
Lampyre - Lampyre - an efficient data analysis and OSINT multi-tool for everyone.
Exploit Pack - Exploit Pack is an open source project security that will help you adapt exploit codes on-the-fly.