To quote the New Vegas Wiki on Quest items you can do this
The SetQuestObject <base id> 0 console command can be used to clear the quest flag from items. This is useful when your inventory is cluttered with items from quests that have been completed and no longer have a purpose.
This is what I usually do to get rid of quest items. To find the item base id you can use FNVEdit and get the base id from there.
We are the hollow men We are the stuffed men Leaning together Headpiece filled with straw. Alas! Our dried voices, when We whisper together Are quiet and meaningless
As wind in dry grass Or rats' feet over broken glass In our dry cellar Shape without form, shade without colour, Paralysed force, gesture without motion; Those who have crossed With direct eyes, to death's other Kingdom Remember us-if at all-not as lost Violent souls, but only As the hollow men The stuffed men.