Nessus - Nessus Professional is a security platform designed for businesses who want to protect the security of themselves, their clients, and their customers.
draw.io - Online diagramming application
Tenable.io - Tenable.io Cyber Exposure platform helps to protect any asset on any computing platform and eliminate blind spots.
LucidChart - LucidChart is the missing link in online productivity suites. LucidChart allows users to create, collaborate on, and publish attractive flowcharts and other diagrams from a web browser.
AlienVault USM (from AT&T Cybersecurity) - AlienVault USM Anywhere delivers powerful threat detection, incident response, and compliance management for cloud, on-premises, and hybrid environments.
PlantUML - PlantUML is an open-source tool that uses simple textual descriptions to draw UML diagrams.