Kali Linux is a Debian-derived Linux distribution designed for digital forensics and penetration testing. It is maintained and funded by Offensive Security Ltd. Mati Aharoni, Devon Kearns and Raphaël Hertzog are the core developers. the link will take you to the official Kali Linux site where you can find downloads to their resources.
PyCharm is another popular Python editor and rounds out my top three. Pycharm is a commercial product, but the makers also offer a community edition which is free and open source under the Apache 2.0 license
Metasploitable is an intentionally vulnerable Linux virtual machine. This is Metasploitable2 (Linux) Metasploitable is an intentionally vulnerable Linux virtual machine. This VM can be used to conduct security training, test security tools, and practice common penetration testing techniques. You will need to have, at minimum, 10 gigabytes of available storage space on your host. Since we are using virtual machines with large file sizes, this means that we are unable to use a FAT32 partition since large files are not supported in that filesystem, so be sure to choose NTFS, ext3, or some other filesystem format. The recommended amount of space needed is 30 gigabytes.
NIST 800-115 - Technical Guide to Information Security Testing and Assessment
The purpose of this document is to assist organizations in planning and conducting technical information security tests and examinations, analyzing findings, and developing mitigation strategies. The guide provides practical recommendations for designing, implementing, and maintaining technical information security test and examination processes and procedures.