A Machine/Forge world, made entirely of metal and steel. Massive factories and workshops, building thousands of pieces of armour and weapons. Huge space/battle stations and shipyards surrounding the planet, constantly creating warships. It would be a planet whose only purpose is to create instruments of war.
Cloning and Military facilities would also be situated there, training and creating new troops at a constant rate, production never faltering. The entire planet would be just one huge factory, churning out every possible item that could help a War Effort.
It would take aspects from many Star Wars planets, such as the looks of Coruscant, the Cloning Facilities of Kamino, the Shipyards of Kuat, the Battle Foundries of Hypori.
There'd be only one place that wasn't full of factories. A city situated in the center of the Forge World, which would house the battle ready troops and Commanders/Generals...
A good planet to have under your control.