Page 126 of the Mindjammer core rulebook states:
“Do I Have to Spend a Stunt to Have a Blaster Rifle?
No, you don’t. Purchasing a weapon as an extra is a way of giving you mechanical advantages like weapon ratings, attack bonuses, or weapon aspects. If you’re not concerned with such advantages and simply want to describe your character using a certain weapon purely for colour, your GM may allow you to do so as part of the gear you automatically get when taking the Melee or Ranged Combat skills.”
But … How much damage does the weapon do if the character picked it up off the ground (or the corpse of a foe) and hasn’t spent the points on it? (the weapon itself is written up on the next page, but costs two stunts.)