Peepdf: https://eternal-todo.com/tools/peepdf-pdf-analysis-tool To explore pdf files if those are malicious or not. python based
Process hacker To monitor system resources https://processhacker.sourceforge.io/downloads.php)https://processhacker.sourceforge.io/downloads.php
TheHive open source free security incident response platform https://thehive-project.org
Caine Digital forensic projects www.caine-live.net
Atomic redteam mitre mapped red team coding and guide https://atomicredteam.io/
Cimsweep IR and hunting operations remotely https://github.com/mattifestation/CimSweep
yara https://github.com/VirusTotal/yara
Any.Run
Hybrid Analysis
GoPhish Phishing campaign simulator
EZ tools https://www.sans.org/tools/ez-tools/
Remnux linux distro for forensic
Devsec.io
mxtoolbox