The Evil Within 2

Since there isn't a guide yet and multiple people have messaged me, here's a breakdown for every weapon in the game and how to get them. I included EVERY weapon in the game, although I'm 99.999% sure one of the pistols don't count.

Melee
Survival Knife: Unmissable in Chapter 2.

Brass Knuckles: Reward for beating the game on Nightmare or Classic Mode difficulties.

Pistols
Semi Automatic Handgun: You get this automatically during Chapter 2 and cannot be missed.

Laser-Sighted Handgun: In Chapter 3, check the parking lot north of the auto repair shop. It will be found on a body by a car.

Silenced Handgun: For doing the side mission “Getting Back Online” in chapter Chapter 7. It is found in the now unlocked item cache in the room with the NPC.

Revolver: To get this, you need to do complete three Flashback Events. They are from finding certain collectibles. You must find File #11 “Torn Psychological Evaluation Report Top” (Chapter 3), Residual Memory #12 (Chapter 7), and File #32 “Computer File: Pit Observatory” (Chapter 11).

Burst Handgun: This is the gun that I don't think counts as it's from a pre-order bonus, but for simplicity's sake I included it. This is from the pre-order bonus “The Last Chance Pack”.

Shotguns:
Sawed-Off Shotgun: Located in chapter 3 in the armory. While doing the side quest “Rogue Signal” (given to you by O’Neal), you will come to a car repair shop. There is an armory located here. Turn on the power and raise the lift to reveal a hatch where the armory is located.

Full Barreled Shotgun: You can get this as early as chapter 6. In the business district there’s a “Post Plus” safehouse. Right outside of the safehouse is a tool shed, in it you find the shotgun. The key to this shed is located in the south of the map, in an dead end alleyway with a military hummer and dead body.

Double Barreled Shotgun: In mission 13 complete the side mission “The Last Step”. This is only available if you did all side missions in chapter 7. Once the mission is over you'll see a cutscene with the NPC. Go into the room where he was and the shotgun will be waiting for you.

Everything Else
Warden Crossbow: You can get this in chapter 3. After exiting the safe house where the chapters start, walk down the road on the left. Walk to the end of the road and you’ll see an armored vehicle with the crossbow behind it.

Sniper Rifle: The earliest you can obtain this is in chapter 3. After exiting the safehouse at the start of the chapter, look for a tall building on the left, just across the street. On the rooftop you find a broken sniper rifle. The parts to fix this can be found in a toolshed in the northwest corner of the map.

Magnum: Reward for beating the story for the first time on any difficulty.

Assault Rifle: At the very start of Chapter 13 after the cutscene plays you can see the Assault Rifle on the couch next to the NPCs.

Flamethrower: Depending on the difficulty this one can be pretty annoying. In chapter 11 there are Harbringer enemies (dudes with flamethrowers) walking around the business district. I believe there were three, but you only need to kill two for famethrower tanks. Fast forward to the Harbringer boss fight (you'll know it when you see it, but avoiding story spoilers). Once you defeat the boss, the broken flamethrower can be found next to the body. Simply go to a bench with the three parts and BAM!

Hey guys! Here's my video guide for all collectibles in the game, weapons included. If you want the time stamps for all of the collectibles, you'll need to open the video in the YouTube browser and check the description. I hope this helps!

Note: Make absolutely sure that you beat the game on nightmare on the save that you get all the weapons on. If you don't, you can't get the brass knuckles, and as far as i know you have to collect all of the weapons on the same save.

Note: You'll need to have completed the two anima events that can be triggered prior to weapon 10 (the Revolver) in order to receive the gun at the end of the third anima event. These can be accessed by picking up a Woman's Diary at 336 Cedar Avenue (Chapter 3, 16:53 in video), and walking into Juke's Diner and activating the residual memory (Chapter 7, 34:07 in video), then interacting with the jukebox. After these, the third one is activated by picking up the file in the pit observatory (Chapter 11, 47:37 in video).

Note: Make Sure you complete all of the Sykes side missions as soon as they appear. Completing "Getting Back Online" will get you the Silenced Handgun and completing "The last Step" will get you the Double Barreled Shotgun.


Chapter 2:
Weapon 1 - Survival Knife - 1:53
Weapon 2 - Handgun - 2:30

Chapter 3:
Weapon 3 - Broken Sniper Rifle - 4:53
Weapon 4 - Warden Crossbow - 5:10
Weapon 5 - Sawed Off Shotgun - 8:30
Weapon 6 - Laser Sighted Handgun - 13:15
Weapon 7 - Sniper Rifle Parts - 14:20

Chapter 7:
Weapon 8 - Full Barrel Shotgun - 36:49
Weapon 9 - Silenced Handgun - 38:24

Chapter 11:
Weapon 10 - Revolver - 48:33
Weapon 11 - Broken Flamethrower - 49:47

Chapter 13:
Weapon 12 - Assault Rifle - 52:20
Weapon 13 - Flamethrower Fuel Tank - 53:33
Weapon 14 - Flamethrower Fuel Tank - 55:21
Weapon 15 - Double Barreled Shotgun - 57:13

Beat the Game:
Weapon 16 - Magnum - 1:05:39
Weapon 17 (Beat on Nightmare) - Brass Knuckles - 1:05:50

This achievement requires multiple playthroughs, as some of the weapons are only given to you once you beat the game. For maximum efficiency, you should beat the game on Nightmare or Classic difficulty, then start a New Game+ on that save file. It doesn't count as "acquiring" the weapons for the sake of this achievement to just have unlocked them at the end of the game, you need to basically be in midst of the game with all of the possible weapons available in your inventory. Also important to note, the warden crossbow on its own is not sufficient. You must collect ALL POSSIBLE BOLT TYPES for the crossbow. I'll list those at the bottom.

Game completion required
Magnum: Awarded for beating the game on any difficulty, will be available in your inventory on New Game+ starting in Chapter 2 after you leave the house where you collect the semi-automatic handgun
Brass Knuckles: Awarded for beating the game on Nightmare or Classic difficulty, will be available in your inventory on New Game+ starting in Chapter 2 after you leave the house where you collect the semi-automatic handgun

Default weapons
Survival Knife: Automatically unlocked in Chapter 2 after completing the Stefano/Guardian segment and reaching Union
Semi-automatic Handgun: Automatically unlocked in Chapter 2 after reaching Union, upon leaving the house that you start out in

Weapons you must look for
Warden Crossbow: CHAPTER 3; Found in the southwest corner of Union behind a Mobius vehicle at the end of the street (marked by a resonance point) *You must also collect all possible bolt types for the crossbow, see a list of those at the bottom*
Sniper Rifle: CHAPTER 3; Broken rifle is found on the roof of the building next to the Union Visitor Center (immediately across from your safehouse starting point)....go up the stairs in the alley and then climb the ladder to get on the roof. Make sure you interact with the body next to the broken rifle, as this will mark on your map the shed to the far northwest where you can find the parts needed to repair the rifle. Once you've picked up the replacement parts, interact with any workbench to craft the repaired rifle. *I have always gotten the sniper rifle in chapter 3 so I cannot confirm this alternative solution, but supposedly if you miss the rifle here, there will be another one available in chapter 13 on the roof of John's Coffee.
Laser-sighted Handgun: CHAPTER 3; Found on a dead body in the parking lot of Union Auto Repair on the west side of the map. You must climb some boxes to get over the fence around the parking lot, then interact with the dead body next to the white car in front of the garage doors. You will immediately be pounced on by a Lost that makes you drop the gun, so make sure you pick it back up after killing the Lost (it will have one of those bright blue glowing points over it to help make it noticeable).
Sawed-off shotgun: CHAPTER 3; Can be found as part of the Rogue Signal side mission or just exploring on your own. In the first house behind the church (322 Cedar Ave) there is a trap door in the back room that leads to a small basement with a Mobius computer. Interact with the computer to enter the Marrow: Armory, then follow the connected rooms until you reach the DW-B03 giant door, entering the small door to the right. Crouch through the hole in the wall, enter another small door, and then the big double doors that require the communicator to unlock. Open the Mobius crates in this room for the sawed-off shotgun and some supplies.
Revolver: CHAPTERS 3, 6/7, 11; This is the most tedious gun to get, as it requires multiple steps through different chapters (and dealing with the Anima lady), beginning in Chapter 3. You must investigate the "woman's voice" resonance in the house at 336 Cedar Ave; the porch light is on to help make this house stand out. Enter the back room and pick up the journal on the table to trigger the FIRST "Anima event" you must complete. SECOND EVENT is in Chapter 6/7 (depending on whether you choose to go directly to the theatre or run around exploring the map after taking exit D5 to the Post Plus) in the Juke Diner building, due south from your starting location at a resonance point marked "Unknown Resonance." Use your communicator to interact with the dead body in the kitchen, then head towards the jukebox in the main room to trigger the second and most annoying of the Anima events. THIRD EVENT is in Chapter 11, when you enter the final big lab room in the Marrow turn right (or turn around, if you've triggered the cutscene showing Hoffman going through the security door) and you'll see a shutter door with the familiar broken panel next to it. Hit the panel with a shock bolt to crouch under the door, then head all the way down the hallway to find a room on the right. Interact with the computer in this room, then leave and run back towards the shutter door so it slams shut and triggers the final Anima event. Once you escape her in the room with all the moving shelves, check the rooms on either side of the next hallway to pick up a file in each (the light in the room will shut off once you do), then go through the last set of double doors to find Classic Seb and acquire his revolver.
Silenced Handgun: CHAPTER 6/7; You must first complete the "Out in the Open" side mission where you save Sykes (the guy being mobbed by Lost in the Krimson Plaza fenced area south of the theatre). Follow him to his safehouse, and then get the "Getting Back Online" side mission by talking to him. After completing this mission to unlock the Mobius crates, return to the safehouse where Sykes is and open the previously-locked crate just inside the door. It will contain the silenced handgun. *Note that these side missions are also required to unlock the mission you'll need to complete for the double-barreled shotgun at the end of this list.*
Full-barreled Shotgun: CHAPTER 6/7; Follow the main street that goes past the theatre and Krimson Plaza to the south, then off to the right is an alleyway area with a body pile and a lot of loot. There will be a resonance point (labelled "Mobius Operative's signature") that leads all the way to the back of the alley area to a dead body holding a key. This key will unlock the red storage shed that is just across from the Post Plus building where you started the area, and in the back of that shed is a Mobius case containing the full-barreled shotgun.
Flamethrower: CHAPTER 11-13; After the boss fight at the end of chapter 11 you can pick up a broken flamethrower from the dead body. To repair it, you will need to kill two of these Harbinger enemies in chapter 13 and collect the fuel tank from their bodies, then go to a workbench to craft the repaired flamethrower. There should be at least 3-4 Harbingers on the map; one spawns straight ahead of you when you exit Post Plus. Another can be triggered near the back of Juke Diner, or near the firey dead-end in front of Sanctuary Hotel. You will need TWO fuel tanks to repair the flamethrower.
Assault Rifle: CHAPTER 13; Right at the start this weapon should be staring you in the face. It's leaned up against the couch with Torres' body.
Double-barreled Shotgun: CHAPTER 13; As long as you completed the other side missions for Sykes in chapter 6/7, "The Last Step" side mission should trigger via your communicator once you head to exit D5 at the start of chapter 13. Meet him at his safehouse to start the mission, then after completing it and seeing him on his way, enter the bathtub room he was just in to find a slim Mobius case containing what should be your final weapon.

Crossbow bolt types
Shock bolt: CHAPTER 3, given to you with the warden crossbow when you pick it up
Harpoon bolt: CHAPTER 3, immediately next to the warden crossbow, leaning against the crate and stuck in the dead man's body
Explosive bolt: CHAPTER 3, inside Union Auto Repair you must activate the fusebox in the back room to turn on the power and then activate the lift with the white car on it, which reveals a trap door in the floor that you can open. (This is also part of the Rogue Signal side mission, but you don't actually have to be following the mission to get into the basement here.) At the end of this basement are two doors - a red door, and the one that requires the key card to unlock. Inside the red door room is a Mobius crate with the explosive bolt inside.
Smoke bolt: CHAPTER 3/4, sitting in an open Mobius crate inside the northern safehouse (if you don't enter this location while exploring in chapter 3, you'll be led here in order to progress once chapter 4 starts)
Freeze bolt: CHAPTER 11, right at the start of the chapter in Torres' safehouse, there's a thin Mobius case to the right side of the room that contains it