Upgrading Weapons
You can remodel your weapons to get much stronger ones, which will cause more damage. Although you can still finish the game with weak weapons, it's better to get the stronger ones.
Below is a list of the items necessary to remodel weapons. If you play alot of Card games early in the game, its possible to get very strong weapons during Disc 1, making Random battles a lot easier. You don't need the magazine to get the new weapon. Just refine some cards (but always keep 1 copy for yourself), go to the junk shop and see what's on offer.
Squall Leonhart
Revolver: 6 M-Stone Piece, 2 Screw
Shear Trigger: 1 Steel Pipe, 4 Screw
Cutting Trigger: 1 Mesmerize Blade, 8 Screw
Flame Saber: 1 Betrayal Sword, 1 Turtle Shell, 4 Screw
Twin Lance: 1 Dino Bone, 2 Red Fang, 12 Screw
Punishment: 1 Chef's Knife, 2 Star Fragment, 1 Turtle Shell, 8 Screw
Lion Heart: 1 Adamantine, 4 Dragon Fang, 12 Pulse Ammo
Zell Dincht
Metal Knucle: 1 Fish Fin, 4 M-Stone Piece
Maverick: 1 Dragon Fin, 1 Spider Web
Gauntlet: 1 Dragon Skin, 1 Fury Fragment
Ehrgeiz: 1 Adamantine, 4 Dragon Skin, 1 Fury Fragment
Selphie Tilmitt
Flail: 2 M-Stone Piece, 2 Screw
Morning Star: 2 Steel Orb, 2 Sharp Spike
Crescent Wish: 1 Inferno Fang, 1 Life Ring, 4 Sharp Spike
Strange Vision: 1 Adamantine, 3 Star Fragment, 2 Curse Spike
Quistis Trepe
Chain Whip: 2 M-Stone Piece, 1 Spider Web
Slaying Tail: 2 Magic Stone, 1 Sharp Spike
Red Scorpion: 2 Ochu Tentacle, 2 Dragon Skin
Save The Queen: 2 Marlboro Tentacles, 4 Sharp Spike, 4 Energy Crystals
Rinoa Heartilly
Pinwheel: 3 M-Stone Piece
Valkyrie: 1 Shear Feather, 1 Magic Stone
Rising Sun: 1 Saw Blade, 3 Screw
Cardinal: 1 Cockatrice Pinion, 1 Mesmerize Blade, 1 Sharp Spike
Shooting Star: 2 Windmill, 1 Regen Ring, 1 Force Armlet, 2 Energy Crystal
Irvine Kinneas
Valiant: 1 Steel Pipe, 4 Screw
Ulysses: 1 Steel Pipe, 1 Bomb Fragment, 2 Screw
Bismarck: 2 Steel Pipe, 4 Dynamo Stone, 8 Screw
Exeter: 2 Dino Bone, 1 Moon Stone, 2 Star Fragment, 18 Screw