Lately, I've been examining the utter pile of technical dog feces that was Gettysburg: Armored Warfare and thinking about a fantasy setting with similar concepts. Really, the visual aspect of the game design was amazing.
So I thought, the Civil War with rayguns and pulp science fiction elements. A cabal of scientists in Europe discovers the secrets of the aetheric fuel of Phlogiston and uses it to create wondrous machines in 1800, discoveries copied on the other side of the Atlantic ocean. Thus, by the time the local tensions break out, the Civil War is fought with the machines of your grandfather's pulp mags.
The standard-issue Union longarm is the Springfield model 1861 Ray Flinger, a powerful energy weapon that flings phlogiston bolts at high speeds towards a target. However, it's lack of accuracy makes it a matter of luck to hit anything beyond 600 yards.
On the Confederate side, the Sharps Wave Rifle is far more accurate with it's focused ray of contained energetic aether that will literally send anything it hits flying apart into it's component molecules. However, mechanical failures will result in the same happening to the user and anybody in the radius of the detonation.