My suggestion would be the shotgun, but rather than the smoothbore, get the rifled barrel and shoot sabots.... they are more accurate than slugs, shoot much flatter, and are easily good for 100+ yards. You can get the rifled barrel either with iron sights or a cantilever mount for a scope. If you want to hunt ducks, geese, or upland birds, all you need is a different barrel and you're in business.
Here's my suggestion for up to 150 yards. I picked up an older model Rem 870
and bought a new Rifled barrel with rifle style sights. I put a B-Square receiver scope
mount on it and an old Tasco Pronghorn 4 power scope on it. Shooting
3 inch 3/4 ounce Federal Sabots I can put 5 rounds in a 1.5 inch circle at 50 yds. Built
this gun 20 yrs ago and it's still my go to deer or pig gun. With this set up, from 25 to
125 yds, it's within 2 inches of zero. At 150 its 3 inches low. Still well within limits for
deer or hogs. At 125 yd it's packing 1600 ft/lbs of energy. Best combination you
can get in my opinion and the reason a lot of Alaskan and African guides carry
one for dangerous game.
Dano