As the title says.

What are the best loots that I should be aware of? Primarily weapons/armor.

Thanks!

Ammunition, power gangers are good for it in the beginning. I usually pick up any weapon and use them to repair one to full health. Explore locations that aren't marked by quests that you pass, you will usually find something unique or helpful.

Where? And what are your needs?

This game is full of loot. It all depends on what you want.

The best loot depends upon your character's specialties. The almighty CZ57 Avenger is worse than useless in the hands of a Melee specialist, the genuinely lethal YCS/186 is pointless to a Guns specialist, the smashing Oh Baby! is merely an oversized club for an Unarmed specialist, the lady of war Annabelle is just deadweight to an Energy Weapons user, & Pushy the magnificent just looks stupid to an Explosives expert.

In general, the worthwhile loot you'll find is: Thrown weapons, ammunition, mines, the enemy's weapons & all-important cold, hard cash. These will allow you to bargain with vendors to get ~ 80% of what you want, at least enough to go seek the truly legendary stuff.

To have the best chance of finding something specific, thoroughly explore everywhere. Walk the Mojave until your character knows it better than they know their own body.

Unique weapons & armors will come in their own time. Some can only be obtained through vendors, quest givers, and companions. In general, the more powerful the weapon, the more dangerous the place it is found in is.

-Nukeknockout

Anything with a good caps to weight ratio... the actual ratio varies with your current amount of caps.

Primm and NCRCF are good for beginning.