[quote=@Xenonia]
I mean, literally the first episode features a cannon, and Peridot's weapon, as far as we can tell, is a giant laser.
[/quote]

Well, fair enough, but let's not get into Gunpowder. I guess we can infer they have Plasma or Laser weapons, if everyone is fine with it. Then go nuts. (Sorry did not think about that)

Edit: Well, non of those weapons were her Gem Weapon, they were created, kind of like her sword. Yes maybe there are guns and Cannons. But they are probably not Gem weapon, hence the requirement in the CS. If you want to make additional weapons, ones that work aside from you Gem, them go ahead.