Recruited him at the skum pitt and its good to have an extra hand helping in battle. But since the last gameplay he has stopped using his shotgun and uses only kicks and punches in battle. Even when i tell him to use 'his best weapon' in the dialogue. What should i do? Should i try giving him a spare shotgun and some shells? How do i do that? Can an npc companion run out of ammo? Cause when i checked his inventory he just had 2 shells and a stimpack but no weapons. That was the first time i checked thru the barter option, but he was using a shotgun before..do weapons show up in their inventory?

Has he the weapon equipped (it shows in his hands) or is there nothing? Yes, the weapon should show in the barter menue.
They need to reload. Giving him something: open the barter menue, take the items you want to give him and click ok.

Well he no longer holds any weapon in his hands.This has happened before but he can also switch to ranged weapons mid combat, i.e his shotgun.But lately in fights i've never seen him once draw his shotgun..I did try doing like how u said but I could not see any shotgun in his inventory although there were just two shells.Maybe he dropped it..Can it happen?..Anyways then I found out the proper way to hand him weapons and gave him a hunting rifle and some bullets. He seems to use that properly now. But i want to ask if he'll switch to fists and kicks again if the ammo runs out.

Sometimes an NPC (or yourself) can suffer a critical failure and fall out the weapon.

And yes, like i said if he can run out of ammo and than starts with the next best
weapon

He can drop it, I don't think it disappears. You can lose ammo in that way though.

Unless your hit chance is very low and\or negative, and you're using a minigun etc... then it might explode in your face :p

Yeah now that i recall, i remember reading a message in the notification box which said something about tycho's shotgun backfiring during combat (or something like that) and that does "1 point of damage to tycho".But i didn't know u could also lose the weapon when this happens....Damn good way to lose some rare weapons if ur using them :(

You just have to be careful and mind your surroundings (and the notification box).

The dropped weapon would be situated right next to the character who drops it, so it's not hard to find.

The weapon can be dropped, or damaged, or lose the current ammo load.

My guess is he ran out of ammo. Don't bother with the barter screen. To give take items, just use the steal skill on him. No matter your skill level you will succeed 100% of the time and they'll never get upset. You can then take or give whatever you want.

If his shotgun wasn't showing up, I'm assuming it was equipped at the time. Equipped items don't show up in a character's inventory.

My advice, give him the weapon you want him to use, give him plenty of ammo for that weapon, click "Use Best Weapon", and don't give him any other weapon (or if you do, make sure he was no ammo for that weapon).

All right then. I now gave him a new hunting rifle with some ammo and he seems to be using that fine..Thanks for the tips all. Just hope he doesn't lose this one...:P