Logic Comparator

Also called a Bug Trap, this is another fantastically useful piece of kit! Its used by clipping the clip (!) onto an IC and setting the unit via dip switches to whether each pin is an input or an output. The unit then compares the IC on the board against a known good IC (which obviously you have to have!) LEDs on the unit light up if there’s any discrepancies between the two ICs. You can also set up ‘cards’ for ICs which get tested a lot so you don’t have to keep setting the dip switches.

This may sound like the most useful piece of kit you can own, but it can only test the ICs themselves. It cannot test for broken traces or faulty sockets, also it can overload outputs and drag down inputs in some circuit designs.
Still its a very good troubleshooting tool.