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Autopsy - "A digital forensics platform and graphical interface of The Sleuth Kit and other digital forensics tools" (sleuthkit.org/autopsy). Use this to view files (it renders text and photographs) and analyze disks/disk images. It can also be used for forensic analysis with added plug-ins.
HexEdit
Super Hex Editor - A hex editor that allows you to redact PII/other information from files.