Not much is known of the origin of the Nuclear Missile, but it is an immensely-powerful weapon, fired ONCE from the Temple of NOD, that is capable of destroying most of your base in a heart-beat. Like the GDI Ion Cannon, the Nuclear Missile can be guided home with a Nuclear Missile Beacon. Once placed, it is not advised to stick around, unless you are a GDI engineer and have nerves of steel, at which point you just walk up and dis-arm the blasted thing.
Similar in function to the GDI Ion Cannon
Remember children, don't play with Nuclear Missile Beacons!