I run around with the SPAS-12, 80% of the time. Use Bling, with stopping power. Have the attachments FMJ and Foregrip on. You'll kill one shot, unless your accuracy is that terrible. I've killed from 15+ ft away with this thing.
SPAS-12, BEAST. The SPAS can kill multiple people with one shot, if they are close enough together, and if you are close enough to them. The spray on that thing is amazing.