Well I have seen this post for quite a time but just didnt have any idea what my One favorite would be ? I have been around guns for a good while and have in the past few years just about given up interest in abunch of other nice guns I own and have just become fascinated with single shots. One reason is due to the many type of actions that have been tried and for a gun with a simple purpose can be just down right COOL !!
I am going to list some of the types of single shot actions that come to my mind and if you remember others , add to them.
Brake Actions, many types some with outside hammers, some hammerless, some that fold , probabley the least expensive and overall most popular type.
The Swinging Barrel action, This type the barrel swings to the side to open the breech to load and extract, example is a Stevens Sure Shot, mostly rimfire rifles.
The Sliding Barrel action, This type the barrel slides forward to load and extract, example the Remington Beals rifle , mostly rifires but has been made in shotguns also.
The Trapdoor Action, this was a clever way to use convert muzzleloading rifles to use metallic cartridges, very simple a top hindged breech block and origanal side hammer , in my opinon a really good way to load and fire a rifle..
The Rolling Block action, Again a really good way to load and fire a cartridge, used from 22 rimfires to 10 ga. shotguns, very versatile.
The Drop block action, Many different types such as the Peabody, Martini, and European designs,
also the Mossberg model L rimrire, and the Ithica model 49 SS rifle.
The Swinging Block action, there were very many of this design at one time the most popular were the Stevens rifles, Favorite, Little Scout No. 44.
The Falling Block action, So many types the list goes on forever, hammer types, hammerless, right now the Ruger # 1 is about the best for what you will have to pay for one.
And dont forget all of the Bolt Action single shots , theres a bunch of them in everything from rimfire boys rifles to big long barreled shotguns.
Theres also the Floberts and other homemade concoctions but I cant think of any type of firearm where there was more ways to load and shoot a cartridge than were made as single shots.