Guerrilla Crate
These can be seen much more than the Weapon Lockers and are sort of smaller versions, but at least they are not just at Safehouses, they are spread throughout the world of Tharsis. They can also be destroyed and if you are close enough to the explosion, prepare to be obliterated into kingdom come. You also only get a certain amount of ammo from each crate and you can only use one once every once awhile. You can also increase the ammo you get from each crate by increasing Morale.