This is a hodge podge of tools that I commonly use for security research, malware analysis, threat hunting, reputation checking, DFIR, and so much more. Please take a look! Some of them are paid for.
If you would like to see a link added, please contact me!
These are in no specific order; however, the resources will be categorized.
https://www.talosintelligence.com/ - Threat intelligence investigations
https://exchange.xforce.ibmcloud.com/ - Threat intelligence investigations
https://www.virustotal.com/ - Analyze files and URLs for reports of malicious behavior
https://urlscan.io/ - Website scanner for finding malicious URLs embedded in a target website
https://www.ssllabs.com/ - Learn about SSL and test public web-server SSL configurations
https://www.shodan.io/ - Search engine for internet connected devices
https://haveibeenpwned.com/ - Database of compromised emails and passwords
https://app.any.run/ - Interactive URL & File Sandbox
https://www.browserling.com/ - Interactive URL Sandbox