Shotguns are ideal close-range specialist tools. They should be a part of your loadout on small to medium maps, but can also be used on larger maps that have close-range engagements. Because Shotguns are usually one-shot kills, you can easily win firefights in tight confines against other weapons. Shotguns are also deadly because you don't need to ADS with them to get a kill - simply aim and fire from the hip.
These weapons are limited at a distance, so you'll need to force a close-range engagement. Perks such as the Agility and Marathon can be used safely to close the gap between you and your target.