Weapon Master

Weapon Master is a campaign achievement/trophy in Call of Duty: Modern Warfare Remastered. It requires the player to get a kill with each type of handheld gun, explosive, and launcher in the single-player campaign.

Pistols

 * USP .45SD: Starting weapon in "Crew Expendable".
 * M9: Starting weapon in mission "Charlie Don't Surf".
 * USP .45: Check the table in first room with enemies in "Charlie Don’t Surf".
 * M1911: Starting weapon in "Hunted".
 * Desert Eagle: Can be picked up from an enemy in "Crew Expendable".

Submachine Guns

 * Mini-Uzi: Many enemies drop it throughout the story.
 * MP5: Many enemies drop it throughout the story.
 * MP5SD: Starting weapon in mission "Crew Expendable".
 * AK-74: Dropped by enemies in "Charlie Don’t Surf".
 * P90SD: Near the end of "All Ghillied Up", located inside the cargo box maze after passing the tanks and infantry.
 * P90: Dropped by enemies in "Mile High Club".
 * Skorpion: Dropped by enemies in "Mile High Club".

Assault Rifles

 * AK-47: Dropped by lots of enemies throughout the story.
 * M4A1: Starting weapon in "The Bog".
 * G3: Dropped by enemies in "The Bog".
 * M4A1 SOPMOD: Starting weapon in "Blackout".
 * M16: Occasionally dropped by teammates in "War Pig".
 * G36C: Can be dropped by enemies in "Hunted".

Shotguns

 * W1200: Found multiple times throughout the story. Can also be dropped by enemies. Can be picked up from the table in the first room in "Charlie Don’t Surf".
 * M1014: Dropped by the first enemy in "Hunted". Also found in many places throughout the story.

Light Machine Guns
M249 SAW: Starting weapon in "Heat". RPD: Located near the table before finding intel #18 in "Safehouse". M60E4: In "Game Over", one of the enemies on the first bridge has it.

Sniper Rifles

 * Dragunov: Found very often throughout the story. Enemies also drop it. Found in the weapons room in "Charlie Don't Surf".
 * M21 SD: Starting weapon in mission “Blackout”.
 * Barrett .50ca;: Starting weapon in "One Shot, One Kill".
 * M21: Obtained in "One Shot, One Kill" after the initial sniper sequence.
 * R700: Starting weapon in mission "The Sins of the Father".

Explosives

 * Flashbang: Part of starting equipment (most missions).
 * M67 Grenade: Part of your starting equipment (most missions).
 * C4: Starting equipment in several missions.
 * M203: Starting weapon in mission “War Pig”.
 * Claymore: Starting equipment in several missions. You also have to put up claymores as part of the story in “One Shot, One Kill”.
 * GP-25: Dropped by several enemies throughout the story. E.g. in first area of mission “All In”.

Launchers

 * RPG-7: Spawned by many enemies throughout the campaign. Also has a fixed spawn point in "Heat".
 * Javelin: Used in "The Bog" as a story item.
 * Stinger: Used in "Hunted" as a story item.