I tried silent kills with a knife, silenced pistol, i tried sniping whilst hidden and no matter what i did i lost huge amounts of rep with NCR and the whole base came after me and killed me, i was about give up when i saw i had a load of C4 and thought, why not?
It was night and the snipers where in bed in their tent, i strolled in, placed some C4 next to each bunk, went to the tent next door, crouched down, equipped the detonator and BOOOM!.
I was expecting to get peppered with lead from all over the base but there was nothing, no commotion, no negative rep, id done it!
I strolled in to their tent, body parts and stuff all over the place, i took all their weapons and equipment then went in to the base and took a few missions, saved and quit.
lol so if you really want to get a NPC's unique weapon or armor etc without losing rep or getting shot up, C4 is the answer.
Just had to share.
Cheers-
Ronin