You could just cheat and use Fallout 4's console commands to enjoy an unlimited bounty of rare guns, but that's not as fun as finding them legitimately. Well, semi-legitimately, because we're going to tell you exactly where they are with a good old fashioned rare weapons guide. Spoilers, obviously, for the locations of these unique guns. (For the spoiler-free version of this article, look at the ceiling while scrolling.)
On this first page, we go over firearms, with energy weapons on page two, and melee weapons on page three. For each we've included screenshots of their locations—click the little arrows in the upper right-hand corner of the images to enlarge them. There are a few more we haven't covered here (these are our favorites), so if you don't find the specific one you're looking for, you might check the Wikia page (opens in new tab).
A modified Fat Man nuke launcher. If you can afford it, Big Boy packs the biggest punch of any gun in the game.
Special Power: Shoots two mini nukes per shot while expending only one piece of ammo.
Where to find it: The Big Boy is refreshingly easy to find. Head to Arturo’s stall in Diamond City. Be ready to pay out the nose for it.
Look out for: Credit card debt.
This powerful combat shotgun has a real chip on its shoulder: with a name like Justice, you know it’s got something to prove.
Special Power: Chance to stagger targets on contact.
Where to find it: Head to Covenant, a perfect little town with perfect people where everyone smiles a little too wide. After you convince the door guard to let you in, look for Penny in the general goods shop. She’ll hook you up.
Look out for: Stepford Wives.
Le Fusil Terribles
This monstrous shotgun is so powerful, the world’s leaders held a summit and agreed that it should be locked away in a secure location forever. Nah, just kidding. Some raider leaves it on a box.
Special Power: Extra 25% limb damage, huge recoil.
Where to find it: The coastal raider camp known as Libertalia is a bunch of boats, some more boat-shaped than others, all nailed together to form a city. Fight your way through every pirate raider until you reach the captain’s quarters at the top of the sunken container ship. Walk in, and “The Terrible Shotgun” will be sitting on a box nearby.
Look out for: Don’t wear power armor on the platforms. You will almost certainly end up in the water at some point, and you don’t want to sink like a brick.
A powerful hunting rifle chambered in .50 caliber.
Special Power: 50% extra damage to Mirelurks and bugs.
Where to find it: Once in the town of Salem, you’ll find a heavily fortified house belonging to the Rook family. Barney Rook will need your help killing a few Mirelurks. Once you’ve gained his trust, he’ll let you inside the house. Inside, you’ll find Barney and his favorite rifle, Reba. In a back room, you’ll find Reba II. You’ll have to kill Barney or pickpocket him for the key, then steal Reba II.
Look out for: Feeling a bit guilty about poor Barney.
The Partystarter is a gross misnomer.
Special Power: 50% extra damage to all humans.
Where to find it: The charming settlement of Goodneighbor is in the dense urban sprawl to the southeast of Diamond City. Walk right in, try not to get on the wrong side of the take-no-bullshit local mayor, and talk to KL-E-0, the saucy robot storekeeper. She’ll gladly sell you a missile launcher that kills all humans, for some reason.
Look out for: A thug nearby tries to extort you for protection money. Tell him to piss off.