A powerful swiss army knife for admin tasks.
And a MUST HAVE for recoveries and emergencies.
No GUI so better have some CLI experience.
But if you have then Finnix reigns supreme.
It comes closest to be truly forensic (doesn't write / touch drives).
Ultra small, fast, bloatfree.
Hasslefree USB installation, no tools / conversion needed, just dd the image file and you're ready to go.
Project seems to be asleep but it's not.
Updates (EFI, kernel, architectures etc) are coming so stay tuned.
But don't wait - make yourself a bootable Finnix USB stick right now.
Better safe than sorry and always be prepared.
Also consider similar projects like GRML and SystemRescueCD to be super safe.
GRML (also very powerful) comes in two flavors, a small one (also CLI only and less tools) and a big one (CLI and GUI and more tools).
SysResCD also has a GUI (Gentoo) included.