Remington Model 870 12 ga pump. This was the shotgun we had in the military and the balance was such that you could fire it one handed like a pistol. Smooth pump action for quick chambering the next round.
And as stated before the noise, flash and sound are such that an intruder will run and not fire back. Plus the fact that a shotgun will be less likely to harm your neighbors property.
Or your neighbors, for that matter.