The p3d models for "aviator_spark_plug" and "igniter_plug" have the paths to their texture as "p:\dz\...." rather than "\dz\...". This makes so that any players that do not have DayZ unpacked on their P: drive will no be able to see the textures (model shows as gray).

Even those these items are not currently used in the vanilla game, they are used in some mods.