For woods bumming I like my spartan side by side coach gun with screw in chokes in 20 gauge. Slugs are accurate to 50 yards and shot will take small game and birds, like having a combo gun in the field. 3" loads even take ducks. It's light, handy, and breaks down and stores in back packs or about anywhere. I think if I was out for survival looking for food, this would be my tool of choice even though I have a 12 gauge side by side, 12 gauge pump, 12 gauge auto, 16 and 10 gauge single shots. Also, for outdoor use in survival situations where you're back packing and carrying your ammo, 20 gauge is more compact and lighter to tote than 12.
By tactical, I guess you mean a fighting shotgun. If two shots ain't enough, a pump shotgun would be my choice and a Mossberg 500 would be my choice of pumps....or Browning BPS. I like the ergos on those guns. I own a Mossberg.
I'm not a tacticool guy and if I wanted a fighting weapon afield, I'd go for a rifle, personally, one of my sub MOA bolt guns that I can connect out past 500 yards with would be my preference. Probably be my Remington M7, light and handy, yet 3/4 moa accurate and I know it well enough to take anyone out to at least 400 yards so long as my rangefinder's battery doesn't go flat. I suppose that would depend on your TEOTWAWKI scenario, though. I'm not really into foil hats and if my biggest worry were law breakers, shooting from long range isn't in the cards, not justifiable, so back to the shotgun.