Mercenaries 2: World in Flames

You can get different weapon packages from supply drop. Just call for one.

Or you can pick up weapons from dead enemies. Or you can supply drop em

To obtain supply drops for your stockpile, you need to enter the factions command posts. Once inside, there will be an option for "shop". You can then buy supply drops that each faction sells.

Weapons can be found from dead enemies and also bought at faction command posts all around (also different factions offer different weapon supply drops, ex. Pirates offer Covert Supply Drop which includes a covert pistol and covert smg)

You can buy weapons from factions base and outpost then call in a supply drop

You can either purchase them from factions then supply drop them or you can get them from dead enemies.

For the supply drops I reccomend the Pirates Supply Drop and the Fuel-Air RPG supply drop.

Pirates supply drop:Shotgun,Machine Pistol and Pistol
Fuel-Air RPG supply drop:Fuel-Air RPG(Kinda obvious huh?)

You can get weapons from dead enemies as many have said and buy them from a faction as a supply drop. (I don't use supply drops and I just beat the whole game with an AK and the hunting pistol when I got it.)