[Pazuzu]

For example, just got an AEM air fuel gauge. Want to check out the color options and ranging and such before going through the whole process of mounting it and connecting it to underdash wiring. So, need a 12-ish volt supply with leads that I can work with.

Or, maybe testing a taillight or headlight receptacle that I just rebuilt, which would be less concerned with how clean the power is, but the amp requirement would be much higher.

Or, testing a sensor and gauge to verify the gauge output based on the sensor voltage (maybe manifold temp sensor for EFI?).

Or the dozens of times that you're wiring a new bulb in place or checking why your MSD keeps blowing fuses, without having to fab up some sort of test leads connected to the battery just to get a basic 12V system checked.

The variable supply would be great for sensor testing...