Since someone was too lazy to explain this fairly good suggestion, i'll write this down.
So, basically, a needler shoots needles. Why not dip them in concentrated floater or radscorpion poison (needs lots of scorpion tails or something from floater) and make a projectile that is able to kill your opponent, even if he just killed you?
Additional, this will give more worth to Antidote and teamwork (Oh fuck guys, i'm poisoned and gonna die, save my gear please, blargh...).
Surely, this mustn't be only poison damage, it also could increase the crippling chance, instead to deal a good chunk of damage in short time - insta- or guaranteed death would be overpowered for this weapon.
So, variant 1: it's a weapon, dealing a lot of damage with delay.
Variant 2: it's a crippling weapon.
What do you think?