Number 3: Power Probe II
At first glance the Power Probe II by Power Probe, Inc., looks like An ordinary test light. Once you connect the Power Probe to the car's battery you have a multitude of testers at your finger tips. With the press of a switch you'll have a hot lead for powering up electrical components like cooling fans, relays, fuel pumps etc. You'll have a ground lead for instantly grounding components.