The guns in this post are exotic because of their rarity, design or both.
We'll start with some older exotics
here is a ten barreled pin-fire pistol
A quick thanks to the National Firearms Museum for the photos
another variation of the same idea
how about a 4-barelled percussion pistol? This one was called a "Duckfoot". They could be had with three to six barrels
Pepperbox revolvers were quite popular prior to the bored through cylinder and metallic cartridge inventions
This revolver served dual duty as brass knuckels
A revolving flint lock rifle
this is supposed to be disguised as a camera?
This appears to a sawed off flint-lock shotgun that has an axe head attached and the stock shaped to maximize the swing power...perhaps the 1st Zombie gun?
some more examples of this concept