I've talked about Zimmerstutzen, or "parlour guns" in a few previous posts. These were, and are, guns that use only a primer charge to propel a ball or other projectile. They go back at least to the 19th Century and the invention of the percussion cap. but reached their peak in the late 19th and early 20thC, with the invention of rimfire cartridges and the CB Cap and BB Cap. The gun seen above is the Guardian Derringer, a modern interpretation of a mid-19thC Zimmerstutzen by Pedersoli. It's in .177 caliber (most period guns were closer to 6mm) and uses a modern shotgun primer rather than a percussion cap. This provides a bit more oomph than a percussion cap, and unlike the cap, pieces of the primer won't fly off on ignition. (This was a big annoyance with the Remington Rider reproduction I owned a while ago- pieces would fly off and hit me in the hand hard enough to break the skin!) You can find this gun at Dixie Gun Works for $255.
Zimmerstutzen began as expensive toys for the wealthy, who could afford a gun with no real practical use, but by the 20thC you could buy an inexpensive BB-cap firing "Flobert" rifle for the equivalent of $42 in today's money:
These were outdoor rifles, although I suppose some were used by those who had a large enough house. They were a bit ore powerful than the percussion-cap propelled guns, and were used by boys for hunting small birds and rodents. I've owned a few, most of which I never fired. One problem with the simple lock mechanism of these cheap guns was that they didn't seal up as tightly as modern actions, and it wasn't unusual to get some gas escaping in the direction of the shooter's face!
Flobert guns weren't the cheapest of the primer-only guns. There have been a few that were cheap enough to be sold as toys for kids. One was the 1950s era Kruger Pistol, which used an extremely small .14grain powder charge- actually a paper cap!- to fire a ".12 caliber lead bullet," more properly called one pellet of #5 bird shot.
That $3 price tag translates to $28 in 2012 dollars, still very reasonable. The Kruger had a few problems, not the least of which was that the corrosive nature of paper caps resulted in the rapid corrosion of the thin metal parts of the gun. Regular cleaning and lubing would prevent this, but how many kids would do that? As a result, working examples are rare today.