Guns of the Civil War tend to fall into two categories: mass produced weapons used in huge numbers by both sides, and experimental or small-run weapons made in limited numbers. But weapons manufacturing was much easier for the Union, as virtually every major foundry and factory was north of the Mason-Dixon Line. Those that weren't had trouble getting raw materials due to the Union blockade of the South.
So the Union was able to crank out over 1.5 million of the iconic Springfield 1861 and 1863 model rifle muskets, along with hundreds of thousands of Colt and Remington revolvers, and smaller numbers of more sophisticated weapons like the Henry and Spencer repeating rifles. But the Confederacy had to make do with rifles imported from Europe, converted flintlocks, cheap knockoffs of the Springfield, and small batches of their own designs.Both sides also experimented with early versions of the weapons that would dominate 20th century battlefields - quick-firing carbine rifles, machine guns, and grenades. All of this added up to massive firepower, and hugely swelling numbers of dead and wounded. Peruse the weapons of the US Civil War on this list and upvote the guns and other devices that were most influential during America's war with itself.
Colt 1851 Navy Revolver
Popular naval version of the Colt, used by both the Union and Confederacy, as well as many other countries.
Colt Army Model 1860
Hugely popular revolver used in mass numbers by both sides.
Reliable and quick-firing repeater rifle used by Union forces at the end of the war.