Speaking of Ghost types, having a Ghost type is probably one of the most solid responses to an underrated threat in my opinion -- Regigigas.
KING BRAZIL
I was browsing through the viability rankings and saw Regigigas in the E ranking, though I really do believe that it is better than that for a few reasons. Back in 4th gen NU, Regigigas was a beast with the lack of Golurk and other common steel types such as Eviolite Metang, Klang, just to name a few. Now, there are obviously many more threats to watch out for as Regigigas often relies on Substitute, Thunder Wave, and Confuse Ray to get itself going, but I want to place significant emphasis on Thunder Wave and Confuse Ray. Parafusion is one of the most legit strategies in crippling opponents in NU as it makes so many slower threats that much easier to sweep with, making Regigigas a great support pokemon when it is not a finisher.
Let's also factor into account Slow Start, which halves attack and speed for five turns...and does nothing about Regigigas' phenomenal 110/110/110 defenses, which is a beast to handle even without defensive investment. However, running max HP is obviously advised due to the nature of Substitute -- but the point is that Slow Start doesn't really cripple Regigigas' ability to tank hits like a champ and is one of the most reliable parafusion spreaders out there. I believe in Fuzznip's analysis of Regigigas in C&C, he mentioned something about the parafusion strategy where it's about a ~60% chance of the opponent not to attack, giving you free turns to move. Compare this to Jirachi's Iron Head in OU or Togekiss's Air Slash in UU. If I could find a real parallel to that kind of luck in NU, this would be it -- except you can set up a sub or do whatever you want while your opponent is immobilized. On the downside, it takes longer to set up this parafusion strategy. But hey, if you're busy wasting turns, that's a good thing for Regigigas because of Slow Start.
Normal STAB is very efficient in NU, and it's proven by threatening sweepers like Zangoose and Tauros, whose sheer power (or sheer force in tauros' case!!) forces many players to run Rock / Steel types to tank a boosted Facade or Rock Climb. Ghosts and Steels are pretty common on most any NU team -- and any NU team that is not running one or the other is completely insane in my books. Being limited to STAB Return is probably a gift for Regigigas simply because Normal STAB is just that good, and Ghosts and Steels can be handled with other various pokemon you can use alongside Regigigas. It's obviously not the pokemon that you slap onto a team just because, and it actually takes some thought to use Regigigas. But given the right support, the benefits you reap for Regigigas often outweigh the amount of support you need alongside it. There are three things Regigigas needs: Toxic Spikes absorption, a Ghost killer, and Steel killer. And each of those three things are very viable for any legit NU team, regardless of Regigigas or not.
I'll name a few Ghost killers off the top of my head: Mandibuzz, Skuntank, Zweilous, Alomomola (for Golurk), Shiftry. Obviously these pokemon have their flaws in killing off ghosts, but the point I am trying to make is that there are many options for a team to use in order to kill off ghosts, as there are pokemon that I haven't mentioned that can kill off a specific ghost or set that it will run depending on the Regigigas team you are trying to make.
..And the same for Steel killers. Charizard, Seismitoad, Sawk, Throh, Primeape, Camerupt. These are all pokemon that can fill other niches other than being a Steel killer (which is a respectable niche in its own right) such as utility, revenge killer, tank, primary sweeper, etc. Making a team around Regigigas is not hard at all, and can be customized in many different ways: you can go offensively with Spikestacking Scolipede for example, or you can go the extremely slow route with pokemon like Muk. Whatever playstyle you choose to run, you cannot deny that Parafusion will help you greatly whether you want to go defensive or offensive.
Back when I wasn't swarmed with work and didn't forfeit all my pokemon, Regigigas was the crux of many of my teams in NU conquest. And when I ladder, I will be using Regigigas, and I have used it with great success. To all of you NUers out there, I urge you to try making a Regigigas team if you haven't already, because that shit is freaking awesome. =)