Wondebus

[I had forgotten where I first sawWonderbus, from Sorcerer Skull.]

This odd, gleefully embellished blunderbus has a brass dial affixed to its side, within handy reach of a "trigger".  Something most blackpowder weapons lack and which allows the Wonderbus to be fired without a punk. This dial my be turned by action of the thumb to one of with two settings:

"Magic" which is used to expel, considerably further afield than one may throw, Boom Boom Balls (mundane black powder grenades, area effect damage, blast open doors, etc).  Or, if blessed with possession of such, to fire the scarce and extraordinary ammunition constructed particularly for this singular arm. These shells have the appearance of large, 1", marbles of varied hues and patterns. Colloquially known among baser adventures as "balls".

"More Magic" a selection, I implore, the wielder make only after rigorous deliberation with their compatriots who will likely be pressed into handling the aftermath of its emanation.  Or, alternatively, every freaking chance you get.  Numerous effects of this stupefying setting have been cataloged.  Most are jovial or amusing nature, many adversely impacting the target, only a few alarming or dangerous to oneself.  The single, reoccurring outcome is the conjuration of copious glee within the Referee.  Roll d1000 and consult your local "Chart of a 1000 Ridiculously Entertaining Magical Effects" 

Some known Wonderbus "Balls":

  Red, Fireball
  Blue, Lighting
  Green, Stinking Cloud
  White Threads, Web
  Black, Sphere of Annihilation
  Purple / Yellow Spiral, Confusion
  Translucent Whiteish, ice-storm
  Clear Hollow, Sphere of Force / Stasis (traps target)
  Multi Colored Sparkles, Chromatic Rays

More Magic effects seen in Gold & Glory campaign.

  Time Stasis everyone but wielder with in 30'. Which was all of party, but not pack of 25 or so Pygmy Lizards busily charging.
  Pack of Pygmy Lizards having irresistible urge to swim upstream and spawn.
  Fleeing doppleganger's last meal being forcefully expelled from its body, in both possible directions.  (The disgorged Pantherman parts, fortuitously tipped off party who this gang of shapchangers ate and replaced, thus avoiding souring an advantageous alliance).
  Spewing several chickens, non-blessed, at the urbane ghasts of Dwimmerhold. Who found it rather borish behavior.
  Caused several slimes to cavort merrily.