Fluke's Awesome Hot or Not Tool. It is compact and can be taken anywhere. Also very mysterious. It's quiet too. Doesn't make loud beeps like many other testers. It has a battery check button which is handy for you to check before use. The lack of an audible alarm is great if you do electrical work where people work and/or run a business. You don't need people watching or getting caught out by all the noise. This is a quality product worth every penny.