My first ever shotgun was the a 12ga Mossberg 500 w/ smooth bore slugster barrell. Nearly 20yrs later I hunt with that same gun. Its the only shotgun I've ever used for deer. Since I've owned it I've replaced the scope on it 1x, and last yr I think I finally wore out the ol' barrell, and replaced it with a rifled barrell. I'm using the winchester BRI sabot slugs in it, and it shoots even better yet. I used to use Brenneki/rottweil slugs with the smooth bore barrell, and its killed alot of deer for me over the yrs. There's probably better shotguns on the market, but for the price you can't beat them.
I also own another 12ga Mossberg 500 with the accu-choke barrell, and mossbergs xx-full turkey choke. I camo'd it up, and its been my turkey gun for the last 5yrs. I picked it up used for $150. With Nitro ammo it'll put 35 pellets in the head & neck of a turkey target at 40yds.
Last but not least I also picked up a used 20ga Mossberg, that my boys use. I have both the accu choke & slugster barrell for it. Open sights. Thats been a good gun as well.