THINGS I'VE BOUGHT: C.H. Hanson Magnetic Stud Finder
This incredibly cheap device requires no batteries and does exactly as its name implies: it finds studs. It also acts as a very small level, perfect for shelf alignment. It’s an all in one package that uses rare earth magnets to find the nails keeping studs in place. It is super simple to use and I would highly recommend it. PLUS, DID I MENTION IT DOES NOT REQUIRE BATTERIES?! Look at the more than 18,000 positive reviews.