Weapons are given by id (or a name from the weapons table). Ammo is added to what the player already has.

ID	Name in scripts	Weapon
2	`weapons.revolver`	Model 12 Revolver
3	`weapons.mauser`	Mauser C96
4	`weapons.colt1911`	Colt M1911A1
5	`weapons.colt1911special`	Colt M1911 Special
6	`weapons.magnum`	S&W Model 19 Revolver
7	`weapons.grenade`	MK2 Frag Grenade
8	`weapons.shotgun`	Remington Model 870
9	`weapons.greasegun`	M3 Grease Gun
10	`weapons.mp40`	MP40
11	`weapons.thompson`	Thompson 1928
12	`weapons.thompsonm1a1`	M1A1 Thompson
13	`weapons.beretta`	Beretta Model 38A
14	`weapons.mg42`	MG42
15	`weapons.garand`	M1 Garand
17	`weapons.kar98k`	Kar98k
21	`weapons.molotov`	Molotov Cocktail

Giving weapons and ammo

player:giveWeapon(weapons.thompson, 200)   -- a Thompson with 200 rounds
player:giveAmmo(weapons.thompson, 50)      -- 50 more
player:giveWeapon(4, 21)                   -- by id: Colt M1911A1
player:removeWeapon(weapons.thompson)
player:removeAllWeapons()

A gun shop

local prices = { [weapons.colt1911] = 150, [weapons.thompson] = 900 }
events.onClient("shop:buyWeapon", function(player, weapon)
    local price = prices[weapon]
    if not price or (player:getMoney() or 0) < price then return end
    player:giveMoney(-price)
    player:giveWeapon(weapon, 50)
end)