Final Fantasy VII Remake - Weapons Guide

Weapons in this game will be your source of tactics and new abilities. You need to raise weapons proficiency by doing what certain weapon requires you to do, so you can unlock its skill. That means you will be able to use learned skill on any weapon you equip. Getting all weapons and learning all abilities will grant you "Weapons Expert" trophy.

Cloud

Buster Sword
Where to find it: Default starting weapon 
How to unlock ability:

Iron Blade
Where to find it: CH3 - You will get it automatically during the story
How to unlock ability:

Nail Bat
Where to find it: Finish Kids on Patrol side quest in Chapter 8 or buy in Chapter 14 in Wall Market Weapons Shop
How to unlock ability:

Hardedge
Where to find it: Buy from the weapon shop in Wall Market during Chapter 9. You can still buy it in Chapter 14 at the same shop
How to unlock ability:

Mythril Saber
Where to find it: Buy from the weapon shop in Wall Market during Chapter 14
How to unlock ability:

Twin Stinger
Where to find it: Purple Item box in Chapter 17 - Sector 0 - The Drum Level 3
How to unlock ability:

Barret

Gatling Gun
Where to find it: Default starting weapon 
How to unlock ability:

Light Machine Gun
Where to find it: CH6 - You will get it automatically during the story
How to unlock ability:

Big Bertha
Where to find it: Buy from Weapons Vendor in Chapter 13 inside Evergreen Park
How to unlock ability:

Steel Pincers
Where to find it: Buy from The Moogle Emporium shop in Secret Children's Hideout in Chapter 14
How to unlock ability:

Wrecking Ball
Where to find it: Complete Subterranean Menage side quest during Chapter 14
How to unlock ability:

EKG Cannon
Where to find it: Buy from Hart for 10000 Gil after scene with Domino later in Chapter 16 Library level
How to unlock ability:

Tifa

Leather Gloves
Where to find it: Default starting weapon 
How to unlock ability:

Metal Knuckles
Where to find it: You will get it automatically from Crab Warden boss during Chapter 5
How to unlock ability:

Sonic Strikers
Where to find it: You can find one in Maco Reactor 5 - B5 during Chapter 7 or you can buy in Chapter 14 in Weapons Shop
How to unlock ability:

Feathered Gloves
Where to find it: Purple Item box in Sewers during Chapter 10
How to unlock ability:

Mythril Claws
Where to find it: Automatically by defeating the Failed Experiment boss in Chapter 13
How to unlock ability:

Purple Pain
Where to find it: Purple Item box in Chapter 16 when you play as Tifa after you fall down while trying to get the keycard
How to unlock ability:

Aerith

Guard Stick
Where to find it: Default starting weapon 
How to unlock ability:

Silver Staff
Where to find it: Buy from The Moogle Emporium shop in Secret Children's Hideout starting from Chapter 8. It is available till end of Chapter 14.
How to unlock ability:

Arcane Scepter
Where to find it: Complet A Dynamite Body side quest during Chapter 9 or buy in Chapter 14 Wall Market Weapon Shop
How to unlock ability:

Mythril Rod
Where to find it: Purple Item box in Train Graveyard during Chapter 11 or in Chapter 14 Wall Market Weapons Shop
How to unlock ability:

Bladed Staff
Where to find it: Steal from the Reaper boss in Train Graveyard - Chapter 11 boss
How to unlock ability:

Reinforced Staff
Where to find it: Purple Item box at the start of Chapter 17
How to unlock ability:

Chronological Order (how and where to get them in order)

Default - Cloud - Weapon 01 - Buster Sword
Default - Barret - Weapon 01 - Gattling Gun
Default - Tifa - Weapon 01 - Leather Gloves
Default - Aerith - Weapon 01 - Guard Stick

Chapter 03 - Cloud - Weapon 02 - Iron Blade
Chapter 05 - Tifa - Weapon 02 - Metal Knuckles
Chapter 06 - Barret - Weapon 02 - Light Machine Gun
Chapter 07 - Tifa - Weapon 03 - Sonic Strikers
Chapter 08 - Aerith - Weapon 02 - Silver Staff
Chapter 08 - Cloud - Weapon 03 - Nail Bat
Chapter 09 - Cloud - Weapon 04 - Hardedge
Chapter 09 - Aerith - Weapon 03 - Arcane Scepter
Chapter 10 - Tifa - Weapon 04 - Feathered Gloves
Chapter 11 - Aerith - Weapon 04 - Mythril Rod
Chapter 11 - Aerith - Weapon 05 - Bladed Staff Steal
Chapter 12 - Barret - Weapon 03 - Big Bertha
Chapter 13 - Tifa - Weapon 05 - Mythril Claws
Chapter 14 - Barret - Weapon 04 - Steel Pincers
Chapter 14 - Cloud - Weapon 05 - Mythril Saber
Chapter 14 - Barret - Weapon 05 - Wrecking Ball
Chapter 16 - Tifa - Weapon 06 - Purple Pain
Chapter 16 - Barret - Weapon 06 - EKG Cannon
Chapter 17 - Aerith - Weapon 06 - Reinforced Staff
Chapter 17 - Cloud - Weapon 06 - Twin Stinger