If I am inside our home, and there is time available to walk to its location, I will reach for a Benelli M2. One of them is positioned where I spend much of my time, and was my duty shotgun, during the final two years of my LE career. We live inside a small, incorporated city, surrounded by a sprawling major city, where any discharge of a firearm has to be legally justifiable, so, “shoot something” would have to mean a human or animal presenting an imminent threat. A 12 Gauge shotgun nicely fills that role. The same Benelli M2, however, would fit the “might have to shoot something” role, if going any number of other places, where the target is undefined, as 12 gauge is versatile, and the Benelli is comfortable to carry, in-hand, or on a simple sling. I keep large-pellet birdshot, two pellet sizes of standard buckshot, premium defensive buck with “flight-control,” and slugs.
The question was not presented as a defensive scenario, or a hunting scenario, so my reply will not go there. We have rifles, from .22 LR to .375 H&H, but even at our rural, wooded acreage, rifle fire has to be very carefully directed.
My “might have to shoot something” handgun would be a .357 Magnum revolver. A specific defensive or hunting scenario may mean a different handgun, but, well, the utility of a .357 revolver covers a wide range, with well-selected ammo. My personal samples are all Ruger: GP100, Speed Six, SP101, and Super GP100.