While I own and use shotguns in all gauges if I had to pare back to only one gun it would be a 12 gauge. A 12 will do anything the smaller qauges can do. I agree with the comments above that another choice as the most versital is just a personal whim. IMO there is an elitist aura that has entered this hobby over the past decade where only "commoners" use 12 gauges.
Jim

The 2nd Amendment IS an unalienable right.