Enter the Voltcraft LZG-1 / Extech CT40!
With this gizmo, you can trace up to 16 wires at once. The system uses a remote unit with 17 alligator clips (16 + one for the common/return conductor).
The remote unit sends a 5V pulse width modulated “square” wave to the main unit. Clip 1 is a ~52% duty cycle wave, and Clip 16 is about 98% duty cycle – at 32 Hz. This allows the main unit to distinguish between each wire reliably – as long as the resistance of each wire is less than 30kohms (which is pretty high).
The main unit also doubles as a DMM. Although it’s not the greatest digitial multimeter, it’s good enough for most applications.
This gizmo is VERY useful for things like debugging home electrical wiring, tracing wires in automotive wiring harnesses, and so on.
You can grab one here:
Saved my life on several occasions!