Because it's not always about pistols, yanno? I am going to use these in my current campaign when it finally reaches Yoon-Suin. Like China in the Renaissance, my Purple Country is less advanced when it comes to guns, but it makes up for it with clever and cruel designs. All of this is inspired by this Wikipedia article about the Huolongjing. Fore more fiery fun, see the post detailing Twenty Gunpowders.
I have included prices with B/X standards in mind, assuming firearms are commonly used in the setting. In Macchiato Monsters, these should be paid for in electrum, gold, or even platinum, depending on complexity and legality.
Barrels 'o' boom. Stick a fuse to it, shoot it from a distance with a magic missile, throw it in a campfire. 3 to 6d6 area damage depending on size, save for half. Add another d6 if stuck in a sack with gravel and nails.
In MM, use the risk die for the gunpowder. Add them together if using several equipment slots, and don't forget to double the damage. A small barrel should be dR12. 100-200GP.
Simple fireworks can be used as signals or to create
distractions. Some produce smoke or fire as well. 20 GP for a noise
maker, 200 GP for a large poisonous rocket.
War rockets are fired from tubes, and loaded with all manners of unpleasantness: shrapnel, lead pellets, darts, or even smaller rockets or little bombs. Treat like a barrel above with the range of a heavy crossbow, and double the price. Used by many bandits to demoralise their targets and shorten the bloodshed.
Rocket arrows do dR6 continuous (as above) when fired with a
tube, or dR8 continuous damage when shot from a crossbow or longbow.
Used by any well equipped army, human or otherwise. 20GP.
Firecrackers are ghost repellents. Blessed at temples, these strings of small fireworks make spirits good and evil flee in disgust. They work as a one-use turn undead at level 3, and can obviously attract a lot of attention from nearby threats. 100GP.
Artillery shields. Mounted on wheels for ease of travel around battlefields and dungeon halls, these door sized steel shields are pierced with hole where guns or fire lances are lodged. It is either used as protection for soldiers, or as a battery weapon operated by a single gunner. Kobolds love these. They shape them with all sorts of dragon motifs. 60 GP.
Flamethrowers. Any big enough gun can be loaded with slow burning gunpowder and metal scraps, turning it into a short range, flesh charring nightmare. Damage is not doubled, but the result of the die is the number of potential target. Poisonous substances can be mixed into the powder. 1-5GP a shot (same as normal gunpowder).
Poisonous gunpowder is only useful in bombs, rockets, and flame throwing devices. A lot of goblin tribes make their own varieties using mushrooms and bugbear feces. Step down the damage die by one, but the targets must save to avoid effects such as blindness, disease, confusion, etc. 10-100GP a shot.