Detectorist

Having the metal detector is essential for collectibles achievements like Where there's muck there's brass and Packed lunch - but fortunately its easy to get one.

There are multiple places where a metal detector will be lying on the ground - but the first is just after you start the game, you'll be in Slatten Dale. Continue down the hill from the telephone box towards the town and keep to the right; you'll see a shallow pool of water with a body in the middle. A metal detector is next to the body which you can just pick right up. And then run away before the leeches eat you alive...