If you need to unload your cargo and transfer it around a shipyard (or anywhere really) quickly and easily, then you need a Quadjumper. The TUG - b13 is a classic. 

Able to attach itself to a cargo container by its magnetic clamps, it then uses thrusters to get it to where it needs to go On Time. 

It can also take 2 passengers if they need to be transferred to a ship along with the cargo. 1 pilot required. It can speed up to 1,150 kph.

The SubPro Corporation also made it capable of being armed. It doesn't come with that automatically, but you can easily add cannons or other firepower to it. 

Freight transport ship.