regarding ship specific weaponry

Is there any way to make a weapon which only affects a certain ship?

For example, is it possible to make a ship which is immune to every weapon but one, while at the same time, making every other ship immune to that weapon?

If that is confusing everyone, think Superman, human weaponry, and kryptonite.

Set the ship as a planet-type ship, and use a planet-busting weapon.

Cool thank you very much.

But wouldn't that let the bullets blow up planets?

Only if your planets are able to be blown up.

Oh sorry