Tacklife Outlet Tester | $5 | Amazon | Promo code QAXI6QOK
Photo: Amazon

Before you do any electrical work around the house, you might want to pick up this outlet tester for $5 with code QAXI6QOK. A series of three lights correspond to a handy chart printed right on the device, telling you if the outlet is properly grounded, has reversed polarity, and more.