ShellShock Live - The Game Wiki

An Item Drop (a.k.a. Ammo Box) is a white box with a green cross that spawns at a random area on the map. It can be used by going over it with the tank and then firing the weapon that it gives the player.

The item in the boxes are random, chosen from the weapons that the player has access to. There is no strategy to picking up or getting the drops.

A tank without a player cannot pick them up. However, Guests and members can.