A few come to mind...the Rem 870, Mossberg 500, or a quality double barrell shotgun, side by side or over under configuration. Since I can only have one, my choice would be a Stoeger "Coach" side by side, double barreled 12 gauge. With only one selection, I would choose one in a matte stainless finish, with fixed Mod and Full chokes. Also in a hammerless, double trigger configuration for simplicity. i have such a shotgun now, and slimmed down my inventory by making a hard choice such as this to keep what I feel is the most versatile and durable one shotgun model. incidently, I kept my pump-action in 20 gauge as a part of my overall battery of must have firearms. I can't think of a more indispensible shotgun to own than a good double barrel 12 gauge as mentioned. Nearly fool-proof, efficient, and effective for both field use and self-defense. Such a "one shotgun" selection is my best advise. I have witnessed no single other type of shotgun survive such long term use and abuse as this. If you can have only one, I say it better last and do everything needed from a scattergun. The same goes for the choice of 12 gauge. If you can only have one, it is certainly the most versatile gauge available. tdv