This is a list of weapons from the concept thread GTA: Liberty City Prologue, along with descriptions of the modifications that can be added to some of the weapons.
List of weapons[]
Handguns[]
Pistol
.357 Magnum
Shotguns[]
Pump-action shotgun
Combat Shotgun
Double-Barrel Shotgun
Machine Pistols and sub-machine guns[]
MAC-10
Uzi
Micro Uzi
MP5
Thompson sub-machine gun
Assault Rifles[]
AK-47
M16
StG 44
Machine Guns[]
M2 Browning Machine Gun (stationary only)
MG 42 (used once in-game)
Minigun
Browning Automatic Rifle
Bren machine gun
Explosives/Fire[]
RPG-7
Bazooka
Grenades
M79 Grenade Launcher
Molotov Cocktail
Flamethrower
Long-range rifles[]
Rifle
Sniper Rifle
M1 Garand
Melee Weapons[]
Brass Knuckles
Police Baton
Baseball Bat
Knife
Butterfly Knife
Meat Cleaver
Machete
Wood Plank
Katana
Fire Axe
Chainsaw
Hack Saw
Hammer
Misc. Items (trash and debris)
Modifications[]
A variety of weapons can be modified, most of them with scopes. Almost every weapon can be silenced, which doesn't count as a modification. The player always has a silencer in his inventory, even if he was busted or wasted. Silencers are only available when a weapon suitable for having a silencer on it is equipped.
Both handguns (pistol and .357 magnum) can be modified. The Magnum can be modified with a scope, which increases accuracy, but slows down the player substantially when seeing through the scope versus aiming normally with the Magnum. It also slows down the rate of fire, but only slightly, by 0.35 seconds.
The list of weapons that can be modified, not including silencers, is here:
Pistol
.357 Magnum
Shotgun
Double-barrel shotgun (can only be turned into a sawed-off shotgun)
AK-47
M16
Rifle
Sniper Rifle
M1 Garand