I was also going to comment, that the winchester 1897 should be the best. Has served in multiple wars. And still used in skeet and duck hunting.Even though I've got multiple 870's and an 1100, I'd still go for the 1897 trench if I had to pick one pump action shotgun because:
1) you can attach a shotgun to a sword
2) it slamfires, and
3) it made people cry about the Hague convention
The winchester model 12 and Ithaca model 37 come second and third. 870's are fourth best on the list, tops, but that's debatable, and I actually like Remington firearms.