Wasteland doctor

 can be found wandering the wasteland during a random encounter. Wasteland Doctors offer healing services and medical supplies. Killing a Wasteland Doctor results in negative karma.

Equipment
Wasteland Doctors can be found wearing a Wasteland Surgeon Outfit or Wasteland Doctor Fatigues and carrying many Stimpaks.

Notable Locations
Wasteland Doctors have been reported around the following areas:

North-East of the Oasis. I've spotted her/him here three times on three accounts.
 * Super Duper Mart, near the entrance
 * Minefield, near the rear entrance to the town
 * Anchorage War Memorial, near the fast travel destination
 * Near a rock outcrop southeast of Raven Rock
 * In the barn behind Vault 101
 * Southwest of Megaton in an rock formation