There are so many makes of shotguns, you are pretty much guaranteed to find one used at a pawn shop or gun store at a good price. Almost all side by side shotguns will have two triggers, one for each barrel. There are also single trigger side by sides which are much quicker and easier to shoot, but generally cost a bit more.
Price Range - Low
If you are on a budget these shotguns are a good way to get started without spending a lot of money:
Stoeger Coach Gun - The Stoeger Coach Gun comes with a short barrel, making it quick and easy to use for shooting through store fronts on the range. Stoeger is now offering the Coach gun with screw in chokes and recoil pads. This is a really good shotgun for the price and will get you shooting at a value.
Stevens 311 - There are a lot of Stevens 311's out there. These shotguns usually have a long barrel that can be cut down to a coach gun length. Most shooters cut the barrel to 22" or 20" in length. Adding a large bead for the front sight gives you quicker target acquisition. This shotgun is a tough old gun at a great value.
A couple of quick modifications will make these shotguns a lot easier to use in competition. One major mod is to hone out the cylinders so that your shotgun shells can be shaken out easily. You can also remove the butt stock and clip the safety mechanism so that it will not reengage every time you open and close the shotgun. This can save valuable seconds on the time clock.
Price Range - Medium
Colt 1878 Double Hammer Replica - As far as hammer shotguns go the Colt 1878 Double Hammer Replica scores a lot of style points, especially for black powder shooters. Unlike most hammer guns, the hammers on this shotgun are very close together making it very easy to cock the hammers simultaneously. Because of this hammer configuration many shooters find this shotgun really helps to improve their time on the clock.
Winchester 1887 Lever Action Shotgun Replica - The 1887 Lever Action Shotgun is another shotgun that ranks high in style. When the lever is open this shotgun loads from the top. The advantage of this method of loading allows you to load two rounds simultaneously. If you buy one straight from the box this feature can be rough at times, however with minor work on the ejectors and the action this feature becomes almost flawless. Coyote Cap Gunworks sells these shotguns with the mods already done, complete and ready to shoot. Alternatively, you can send him your own shotgun and he will do the work for you.
Stoeger Coach Gun Single Trigger - For a few dollars more than the standard Stoeger Coach Gun you can get the Stoeger Coach Gun Single Trigger. With the flick of your finger you can unload both barrels with one trigger. This is a really great shotgun at half the price of most single trigger side by sides.
Winchester 1897 Chinese Replica - In recent years there have been a few Chinese companies reproducing this shotgun. If the 1897 pump is what you're looking for and you don't want to shell out the rising cost of an original Winchester 1897, this is a great option. The majority of these come with a short barrel. A couple of modifications, such as a large front bead sight and minor action work, make this a great pump shotgun for the value.
Price Range - High
SKB Side By Side Single Trigger - Although recently discontinued, the SKB Side By Side are quite easily found, both new and used. This is a single trigger that features a low profile lock action. This gun is very attractive and is a higher quality shotgun than the Stoeger Single Trigger. Still, you may have to polish and/or hone the cylinders for smoother shell ejection. Most of these come with a longer barrel that you may opt to cut down to your preference.
Winchester 1897 (Original) - The popularity of Cowboy Action Shooting in recent years has really driven the price of original Winchester 1897s up. Being that it is the ONLY pump shotgun model that is SASS legal, these are in high demand. The Winchester 1897 is a labor of love. If you love to shoot these shotguns it is best to keep at least three on hand - one to shoot, one as a backup in the gun cart, and one in the shop! There are a lot of small parts on these shotguns and they tend to break quite often. In the right hands, however, this shotgun is very fast. Just throw a shell in the ejector port, hold the trigger down, and pump to slam fire. Slam firing is a feature built in to this shotgun by John Browning, which makes it very fun to shoot!
Browning Single Trigger - The Browning Single Trigger is my personal favorite Single Trigger Side by Side. This gun is not only of superior quality but it is also very attractive. Most of the receivers have engravings and the wood furniture has checkering and comes in a variety of colors. The shell ejector is even lower in profile than the SKB. Your shotgun shells will practically load themselves! In my opinion, this is the best side by side shotgun for competition shooting.
Coyote Cap Gunworks