What, so Nuclear Torpedoes aren't enough of a weapon for you? They blow up pretty good after being used.
I can see a couple of things that would approach your intent, though the actual "use it, lose it" part isn't going to work.
- Make the weapon very fragile, with a low hitpoint amount and nasty abilities (Armour comes to mind). It will be destroyed pretty quick that way - if someone on the other side is firing, that is. You could add a huge penalty to defence, just to make sure it *will* be destroyed as soon as something targets it, and the player will be glad the weapon is gone.
- You could also use a reload time of 30, just to make sure the weapon isn't going to be very useful. This could be used in addition to the effect outlined above.
- You may also wish to make the weapon cost a huge amount of supplies, though this will be difficult to handle. Even weapons that don't need any supply cannot fire without supplies, so you cannot just set an insane value to the one-shot weapon and make all other weapons use no supplies. Probably the worst idea, unless you plan to use drones.
- You could mount the weapon onto drones, and give said weapon an insanely high supply requirement. That way, the drone will fire the weapon once, and then be destroyed. You can then boost your weapon if you are so inclined, since drones aren't particularly the most dangerous hull out there.