Gunnspier

Weapon (any polearm), rare
  “Stab, bang, hope.” If consulted, these are the instructions any kobold will give on using a gunnspier. With a lengthy reload time and complete lack of accuracy, this matchlock-augmented polearm is usable at only one range: point blank. It also comes with a lovely ribbon and neat basket to hold all your spare shot. Cute.
  You have a +1 bonus to attack and damage rolls made with this magic weapon.
  Point Blank Shot. When you hit a target with an attack using a loaded gunnspier, you can use a bonus action to pull the trigger, firing a plum-sized leaden ball at the target. The attack deals an additional 2d8 bludgeoning damage.
  Backfire. When you use Point Blank Shot and roll an 8 on both of the additional bludgeoning damage dice, the gunnspier backfires. Each creature within 10 feet of you (including you) must succeed on a DC 15 Dexterity saving throw or take 4d6 piercing damage as shrapnel erupts from the weapon.
  Reload. As an action, you can reload the gunnspier.
  Very rare variant: Three weapons in one, this upgraded gunnspier can slash, shoot, and bite. The pneumatic-powered dragon’s maw can run along the length of the gun's barrel before biting into a target skewered by its point.
  Increase the attack and damage bonus to + 2 and the damage of Point Blank Shot to 3d8. Remove the Backfire property and add the Chomp property:
  Chomp. When you hit a target with an attack using the gunnspier, you can use a bonus action to cause the jaws to shoot forward and bite into your target, dealing an additional 1d10 piercing damage to it as part of the attack.