I have a bolt action slug gun with a ported barrel when I shoot from a stand or tower. If you are going to be hunting in heavy cover, I would recommend a pump or auto. For a pump, I like Remington 870 and Mossberg 500. Make sure to get one capable of shooting a 3" shell. Be aware that some have a rifled barrel and some have a smooth barrel. Don't confuse the description of rifle sights for a rifle barrel. If you are going to be putting an optical sight on a gun that is not a single action or bolt action, I recommend getting a barrel with a cantilever mount.
Rifled slugs can be more expensive than rifle ammo. Sabot slugs (for a rifled barrel) can be a few bucks a pop. Here is a tip. If you do decide to get a slug gun, buy one or two boxes of the same lot (box of 5) of three or four manufactures when they are on clearance after the season is over. See which proves to be most accurate. Personally, I like Lightfield EXP (I use 2 3/4 with a 1 1/4 once slug). I started using them years ago because they were the least expensive sabot round at the time (no longer true). This round really knocks them down.
Be aware that wind really affects a slug. Just a 10 MPH wind can push the slug 6 inches at 100 yards. When you sight in the gun, use a distance of 50 yards to set the windage (make sure it is perfectly centered vertically with the bullseye). Use the longer distances to adjust the elevation.