Over the course of a few years I spent a lot of time in a secure environment in a DoD facility to which I had to travel multiple times for a project. The environment, a maze of cubicles filled with computers, had been installed inside a historic building. For historic preservation reasons, the exterior windows were kept as built. For security reasons, there was a sheet of plywood painted white inside all of the windows. The building allowed no natural light to enter and emitted only a diffuse glow. It was a miserable place to spend long days, illuminated only by flickering fluorescent light.
We had some serious storms come through while I was there. Almost all of the permanent residents went home. As I was a visitor and there just for as long as it took me to fix some problems, I was encouraged to stay and work late. I was assured that we would not lose power because the building had been recently equipped with a generator.
A storm came through and the building lost power. It was almost entirely pitch black in the building full of computers, which all went dark, fans and disks suddenly silent. A few were connected to uninterruptible power supplies, which beeped until they drained the batteries dry. A small fraction of the emergency lights came on. Most were in disrepair and never lit up. It turns out that in a secure environment, one has to make special arrangements to have someone inspect and maintain the emergency lighting. We heard the generator spin up. Still no computers, no lights.
In the darkness, one little nook came to life. This comparatively well-lit oasis contained the coffee pot, microwave, and refrigerator. Apparently this organization considered only one piece of equipment important enough to be connected to the generator. We thereafter referred to it as the mission critical coffee pot.