Slurpuff got nifty in Hidden Type with the coming of ORAS, gaining Drain Punch. Not much else, but that's OK, in Hidden Type it doesn't need much else -Dark and Steel are extremely popular types, so much so that you can often Drain Punch into Pokemon that would normally resist it and have a reasonable expectation that it will be a neutral hit. Meanwhile, Pokemon that add Ghost typing are generally obvious, and generally don't want to be hit by Play Rough, certainly not at +6 -it's a OHKO on Eviolite Chansey, and Mega Tyranitar (Usually Ghost, but sometimes Flying) can only really pray for Play Rough to miss if Slurpuff is on the rampage. Dragon is another popular type to add to Pokemon, including the likes of Clefable, Skarmory, and Azumarill, so Play Rough isn't simply "your other, stronger STAB", it's legitimately murderous on much of the tier.
Of course, Slurpuff needs to get a shot at Belly Drum, and even though Fairy/Fighting is an excellent offensive combination with few things that wall it (Gengar is one of the only things that normally does, and it defaults to adding Dark in Hidden Type, ruining its resistance) it's a surprisingly iffy combination defensively, having all the weaknesses of both types and no particularly complimentary aspect, which makes it difficult to switch in and start the rampage -you have to select with care. Furthermore, even though most Skarmory are incapable of walling Belly Drum Slurpuff (I have never seen Ghost Skarmory, personally, nor Poison Skarmory, nor Bug Skarmory, and probably never will see any of those save perhaps Ghost), it's probably running Sturdy and can Whirlwind you out, Drill Peck you for severe damage, or spring a surprise Counter for a clean OHKO, so you need to do something to break its Sturdy before you try to bring in Slurpuff against a team carrying Skarmory. Ferrothorn is also worth watching out for -it often runs Ghost typing, in which case you're not Drain Punching through it, and it can either cleanly destroy you with Gyro Ball, or toss Leech Seed and wait you out, maybe slip in Stealth Rocks.
Oddly enough, Slurpuff actually gets Heal Bell/Aromatherapy (Seriously, both of them), so Slurpuff can also laugh off Burns/Toxic if you like, potentially helping the team in the deal, or you could "all-in" and run Facade as a way to push monstrous damage through when hit with one of those -of course then it becomes trivial for a Ghost to wall you, so Heal Bell might be the better option. In any event, Slurpuff can push past even fairly competent Stall Pokemon due to Heal Bell or Facade, which is quite nice. Alternatively, if you're worried about Ghosts (Including the common Ghost Ferrothorn), you can run Thief -this is risky, because Unburden deactivates if you gain a new item, and there's no guarantee that you'll steal a consumable item, but it can be worth considering just to prevent the rampage from losing all its momentum, and it may surprise the opponent.
A key advantage Slurpuff's offense has is that a lot of Pokemon in Hidden Type select a type that resists Stealth Rock, which means Fighting, Ground, or Steel -Ground is the only one neutral to both Fighting and Fairy, and Ground is honestly an iffy type for most Pokemon, defensively. (Two resistance, one of which is to Poison, one immunity, and three weaknesses, two of which are to excellent types) So it's surprisingly rare for anything on the enemy team to actually resist-or-better the two types paired together. This makes it very difficult for most teams to actually stop the rampage once it gets going without leaning on priority, and priority is a lot less popular in Hidden Type than in a lot of metas, perhaps in part because double weaknesses almost never make it on a team to be punished by priority. (Crawdaunt being a notable exception to both ends [no Fairy priority, though, unless you count Sylveon Quick Attacking], but Aqua Jet is 252+ Atk Life Orb Adaptability Crawdaunt Aqua Jet vs. 52 HP / 0 Def Slurpuff: 135-161 (42.4 - 50.6%) -- 1.6% chance to 2HKO, which requires Sitrus Belly Drum Slurpuff suffers other damage before it will be a KO -and most Crawdaunt are running Fighting, and therefore Drain Punch will substantially heal Slurpuff)
Slurpuff appreciates support, such as hazards to break Sashes and Sturdy, but is not difficult to fit into a straight offense team so long as you maintain awareness that Slurpuff needs to be switched in on something it is reasonably safe from (Beware Gyro Ball in particular), that you keep in mind what Pokemon on the enemy team can potentially laugh at its attacks, and you are ready to pave the way in terms of breaking Skarmory's Sturdy and similar. The trickiest thing is accounting for those Pokemon that might run Ghost, but not necessarily -Ferrothorn runs Ghost, but more often it runs Water, and it can be easy to be lulled into thinking every Ferrothorn is HP for you if you keep encountering these Water-typed Ferrothorn. A wasted Drain Punch can be the end of the rampage... and if that's immediately after you Belly Drummed? Yeah, bad outcome. Otherwise though, Slurpuff is certainly not a Stall team's preference, except perhaps as an ace-in-the-hole stallbreaker, but doesn't have particularly demanding team construction requirements.
Notable threats include...
-Skarmory, for reasons previously described.
-Ferrothorn, specifically Ghost typed, as previously described.
-Fire or Poison typed Clefable, particularly if they're Unaware. (Poison Clefable is not something I've seen, but Fire is something I have fought and run, and is fairly effective) They also resist Thief, bonus points.
-Togekiss in general. Fire type Togekiss will doubly resist Drain Punch and resist Play Rough and strike back with super effective Air Slashes or Dazzling Gleams, and Steel type Togekiss will still resist Drain Punch too. Not only that, but even Thief is ineffective against them all. If you see a Togekiss, take it out or severely weaken it before kicking off the rampage.
-Chandelure. It's most common addition is Grass, and +6 252+ Atk Slurpuff Play Rough vs. 0 HP / 4 Def Chandelure: 252-297 (96.5 - 113.7%) -- 81.3% chance to OHKO means that with even relatively modest bulk Chandelure can potentially reliably survive and hit back for damage -and its damage is excellent, of course.
-Fast Scarfers. Ideally you will have scouted them out, taken them down, or at least Knock Offed their Scarf. If it's above around 100 Speed and is a credible Scarfer, watch it -and beware lower Speeds if you're running less than max Speed EVs, of course.
-Oddly enough, Toxicroak. It almost always runs Dark, but a combination of Fake Out+Bullet Punch does decent enough damage, and with Poison Touch there's good odds you'll end up Poisoned. It also a credible Sasher, so if you don't have hazards up it may simply Fake Out, and then Poison Jab for a KO. (252+ Atk Toxicroak Poison Jab vs. 52 HP / 0 Def Slurpuff: 284-336 (89.3 - 105.6%) -- 37.5% chance to OHKO. Even if you heal to full by Drain Punching it, it may still KO you with the Poison Jab, and that will have been three rolls at trying to Poison you if it's running Poison Touch)
---
Pretend I had a good closing statement.
I can't recall playing an OM in which I saw a lot of evidence that the other three were good, and I know haven't used them myself, so I'll be skipping the rest of this round, alas.
EDIT: At request
Slurpuff @ Sitrus Berry
Ability: Unburden
EVs: 4 HP / 252 Atk / 252 Spe
Adamant Nature
IVs: 30 Def / 30 SpA / 30 SpD / 30 Spe
- Drain Punch
- Play Rough
- Heal Bell/Facade/Thief
- Belly Drum