On this question somebody said some companions will collect items on their own. Is that true (and, if so, which companions collect which items)?
Companions won't collect items for you unless you specifically tell them to loot an object.
Companions however do sometimes randomly give you "gifts" when talked to.
- Strong gives raw meat.
- Piper gives pre-war foods
- Hancock gives drugs
- Codsworth gives water
- Curie gives stimpacks
- Cait gives booze
- others give ammo related to the weapons they use (X6 and Danse give energy ammo while McReady gives ballistic ammo)
Only Preston and Dogmeat don't give anything as far as i know.