Fallout 3 Unique Weapons: A3-21 Plasma Rifle
A3-21 Plasma Rifle is the Fallout 3 Unique Weapon that replaces the plasma rifle. It's probably the best energy weapon in the game and is my favorite weapon. So where can you find the A3-21 Plasma Rifle unique weapon?
A3-21 Plasma Rifle
Damage at 100%: 38
Ammo: MC cell
Location: Rivet City
How to get A3-21 Plasma Rifle
You get the A3-21 plasma rifle from Harkness in Rivet City. Before he gives you his rifle, you must go through the Replicated Man quest first.
You start the quest by talking to Dr.Zimmer in Rivet City's Science lab. He will ask you to find his android.
I won't go into the entire quest here, but you eventually discover that Harkness, the security chief of Rivet city, is the android.
Once you discover that Harkness is the android, you need to confront him about it. You will then re-activate his buried memories.
Tell Harkness that you want to "take care" of Dr. Zimmer yourself and he will give you his A3-21 Assault Rifle.
Optional: You can get an enhancement from Dr. Zimmer if you tell him that Harkness is the android. The enhancement increases you chance to hit in VATS, but it will give you bad Karma for giving Harkness away.
Once you have the A3-21 Plasma Rifle unique weapon, you should start investing points in your energy weapon because it's the best weapon to use. It's deadly accurate and although it may seem to have less damage than the Xualong Assault Rifle on paper, it actually packs way more punch.