Containers (i.e. refrigerator, metal box, etc - including corpses and hollowed-out rocks) that have one or more of these items inside will also be highlighted. Once the items are removed, the container will no longer be highlighted.
Appropriately, the Courier's body counts with this perk, by dying while aiming down sights.
PC Playstation 3 Some killed creatures such as lakelurks will be highlighted despite their bodies not containing anything they can be looted of. In the case of lakelurks this may be due to their shriek "weapon" they carry, which is classified as a weapon with ammunition but cannot actually be obtained. [verified]