Despite being a stealth-focused game, there is a trove of weapons to be found in Metal Gear Solid Delta: Snake Eater, both lethal and non-lethal. While many of these can be found in Virtuous Mission, you will end up losing them all again by the time you embark upon Operation Snake Eater.
This guide for Metal Gear Solid Delta: Snake Eater is a complete listing of all weapons in the game as well as where they can be found.
Survival Knife
From the beginning
Fork
Progression unlock in Groznyj Grad Torture Room in your cell
Cigarette Gas Spray
Graniny Gorki Lab B1 West: search the offices to the right of the point of entry
Handkerchief
Graniny Gorki Lab B1 West: to the left of the TV, search the corner locker nearest to the blackboard
Mk22
Virtuous Mission: from the beginning
Operation Snake Eater: as a progression unlock from EVA
M1911A1
Operation Snake Eater: as a progression unlock from the beginning
EZ Gun
On Very Easy difficulty with unlimited ammo and suppressor
Also by collecting all 48 plants and animals for the Markhor title
Single Action Army
Progression unlock in Groznyj Grad Torture Room and then upon story completion for new game plus, available after retrieving your backpack
Scorpion
Groznyj Grad Weapons Lab: East Wing: inside a locked storeroom on the ground floor at the northern edge
Patriot
Upon story completion for new game plus, available after retrieving your backpack
XM16E1
Virtuous Mission: hidden in a recessed space under the northern end of the bridge in Dolinovodno
Graniny Gorki Lab Exterior: Inside Walls: inside a small structure in the corner of this area
AK-47
Rassvet: head upstairs inside the ruins and find it at the top of the stairway
Bolshaya Past Base: in the storeroom of a small building to the north-east
M37
Virtuous Mission: hidden amongst metal crates in the ruins in Rassvet
Chyornaya Peschera Cave: head right from the beginning and into a small area at the end
M63
Svyatogornyj East: leave Svyatogornyj West from the east to reach here, and then find the storeroom in the large central house, with the weapon hidden amongst crates
SVD
Virtuous Mission: hidden to the right of the first group of enemies in Dremuchij North
Ponizovje West: after the boss battle with The Pain, continue left in Ponizovje South along the river till you arrive at the docks and a building nearby with a yellow door leading to a storeroom
Mosin Nagant
Sokrovenno: rewarded as a spawn after performing a non-lethal takedown of The End
RPG-7
Krasnogorje Mountainside: check the right-most structure near the AA in the eastern section of this area
Torch
Chyornaya Peschera Cave Branch: hidden behind the twin waterfalls
Claymore
Bolshaya Past South: disarm a claymore by crawling into it from the rear
TNT
Bolshaya Past Base: in a building to the north-east
Book
Graniny Gorki South: head left and carefully navigate around the tripwire
Magazine
Simply exhaust an AK-47 magazine completely
Mousetrap
Bolshaya Past Base: search under the beds in the main building as well as the food storage building
Grenade
As pickups, or loot from holding up enemies
WP Grenade
As pickups, or loot from holding up enemies
Stun Grenade
As pickups, or loot from holding up enemies
Chaff Grenade
As pickups, or loot from holding up enemies
Smoke Grenade
As pickups, or loot from holding up enemies
Those are all 28 weapons to be found in Metal Gear Solid Delta: Snake Eater.