I wanted to start an anti-metagame discussion- I think the best way to start this is through sharing my team. Only the pivots on this team are strictly OU, and every member of this team arguably all fill niches in the metagame which I think would be valuable to this discussion.
Fck Fairies (Toxicroak): Essentially, specs Ash Greninja is one of the most terrifying threats in OU period. Toxicroak walls him completely with AV, dry skin and EVs invested in HP and attack (will do an EV breakdown later). Switch him in on AG attempting to revenge kill with water shrunken and hit back with drain punch. Toxicroak also has brilliant matchups against most rain teams and Tapu Bulu (In fact he is arguably brilliant against all Tapus given AV- even lele, the reason for this is explained later.) As Toxic spikes have become more common in this generation given the staple of Toxapex, having a poison type has become increasingly attractive. Drain punch makes him a good way to deal with mega/regular T-tar, another reason which makes me question why how is he not even OU.
Morover, Ice punch 2HKOs Lando T (even after intimidate) which is important because of how common Lando/zygarde and other ground types are for toxicroak. Gunk shot is a must, as is sucker punch which reliably kills mega alakazam, Another thing fck fairies does well is threaten heatran. AV guarantees he will live a magma storm or earth power and drain punch recovers his health afterwards. 99% of the time, the opposing player assumes you will swap out and will take the chance to put up rocks. Their mistake. Another mon which Fck Fairies does well against is belly dance Azumaril- a right pain if you aren't prepared for him. Fairies in general do poorly (like Clefable) hence the name, but do be careful of misreading Tapu Lele.
EV breakdown: HP 198, ATT 248+, SPD 8, SPE 56
Bird Jesus (Mega Pidgeot.) This is my designated lead and hurricane spammer in one. A timid nature and max investment into Speed and SPA give it the important speed of 375- something extremely important. Whilst outsped by leads like tapu koko and aerodactyl, bird jesus is outsped by scarfed lando-t. Given how common a lead of lando-t is (especially since most players turn 1 resort for U-turn), if you pit him against bird jesus, you can scout which item he is holding. U-turn turn 1 is the standard play- if lando t is scarfed and uses stone edge, you can revenge kill easily, if he uses U-turn you can prepare in the future accordingly for that threat. If you outspeed, you can at least see if he is rocky helmet or leftovers- a safe switch in is usually rotom wash. On bird jesus I pack heatwave (for ferrothorn and other pesky grass or steel types such as Kartana- he will also live scarfed Kartana's sacred sword), hurricane for spam, and a reliable way to kill mega venusaur, U-turn for momentum, and defog. (Rocks hurt this team a lot despite bird jesus being the only one who takes any significant damage from it- this is because to get the best out of this team, you will need to make lots of reads, be comfortable pivoting out and taking risks.) mega pidgeot is also a solid switch in for jirachi (heatwave and U-turn are all nice options), and again you can use him to scout out whether jirachi is scarfed. Bird jesus is also my favourite way to deal with mega medicham, gallade and other pesky fighting types.
Xbox (rotom wash) this is my go-to if I want to burn something. Max SpD and HP investment, with it being speed crept to allow other rotoms to outspeed it. (A common situation is two opposing rotom washs volt switching on each other- he can take a volt switch fine, and I like the strategic benefits of a slow pivot.) Neither heatran, any of the Charizards or lando T enjoy a hydro pump (with no investment) to the face. Generally xbox is a reliable switch in for most things in the metagame. Slap on a sitrus berry (usually my go-to switch in for a Z move- so regaining health back is crucial.) The other role played by Xbox is that he is my other defogger (normally is my primary one, and Bird jesus is an extra contingency- rocks/hazard control are the best way to counter this team.)
Pulling machine (magnezone) This is probably a staple to most anti-meta teams- since the release of magnet pull, magnezone has been fulfilling the same niche- trap and kill skarmory. However, he has other roles to play in this team. Firstly, outside of rain, he destroys ferrothorn. Celesteela doesn't do much better (unless packing Firium Z), and doesn't appreciate him (especially when it is stall/leech seed celesteela.) The other main purpose of magnezone is to kill Toxapex, something which is a right pain to any team. I use hp fire, volt switch, t-bolt and flash cannon on this mon, and invest in HP, SPA and Speed (sped crept to outspeed skarmory- take the EVs from HP) and slap on specs. A common situation is when Magnezone is switched in to take a toxic or a scald from Toxapex and looks to pivot out with volt switch. That is the obvious play. 9 times out of 10, the other player will hard swap out into lando t. That's when you make the ballsy play and hit him with flash cannon on the switch. Depending on EV investment on the opposing mon, its a safe bet that it will do around 70-80%. After that, hard swap yourself out into rotom- used best when the opponent is scarfed lando.
Another purpose of magnezone is that specs volt switch hurts, a lot, even when resisted, so once you have removed lando-t, feel free to spam volt switch with rotom and magnezone and chip your opponent down for your cleaners. Moreover, the ability to punch holes in magearna, mega mawile and mega scizor is also pretty cool (although AV magearna is bulky as hell.) Magnezone also is used to slaughter alolan ninetales, even with aurora veil up.
Big Sexy (Mamoswine.) This, like magnezone is well known to be another staple on anti meta teams. I actually got the idea of using this mon from my old VGC team where I used it on a trick room team with Mega Abomasnow, Alolan Marowak and Mimikyu. Ground and ice are especially good stabs to have in an OU metagame full of things with a 4 times weakness to them.
Earthquake is a given, as is ice shard. Ice shard makes mamo a great cleaner (not its only purpose though.) Knock off (for chansey and other pesky eviolite abusers) and stealth rock (to give Charizard Y and Volcarona a harder time) finishes off this set. However, the most important part of this mon is its item- focus sash. This is my usual get-out-of-jail-free card if I had let something scary set up. For example Mega Charizard X dancing up can be terrifying given its wallbreaking power. That's when you use Mamoswine to suck up the flare blitz, live and kill him with EQ. This is the main reason I put defog on both rotom and bird jesus- mamoswine can only feasible use ice shard if his sash is broken given his low speed.
Big Lobster (Crawdaunt.) I'm really surprised he isn't OU given my (wholly unbiased) opinion that he is the greatest cleaner in OU. STAB boosted aqua jet with adaptability and a choice band will reliably clean most of the tier- special mentions to lando t, Charizards, volcarona, victini, blacephon, gliscor, excadrill (you get the picture.) Knock off is equally as scary and will probably kill most of the tier on the switch. Reverse him especially for chansey and toxapex (depending on EVs, knock off can kill.) Superpower and crabhammer round up the set, but knock off and aqua jet are all you really need. I've sped crept my one to outrun heatran, although most of the time, if the opponent sees this scary MOFO, they tend to yeet out and just forfeit. It's dark typing helps with scarfed or specs lele, given the opportunity to save toxicroak from being obliterated by a terrain boosted psychic/shock
Weaknesses of this team:
It's very Gen 4 reminiscent (obviously bird jesus was god awful then given no mega form), given the mons and no Z move but a flaw of this team is that it simply lacks any fairy type coverage which makes mega sableye a threat. status also sucks for this team given that there are no clerics available. A burn on mamo or crawdaunt can easily end your game. Charizard Y is another big threat- there are no safe switchins for him- rotom wash can't survive 2 solarbeams, and everything else doesn't really like a sun boosted fire blast. The only reliable way to deal with it is to get rocks up from mamo and to revenge kill him. Hawlucha is also not liked, but he is not the most common, and you can use mamo to partially deal with him. The same applies with mega lopunny (a major pain in the ass) and Kyurem black (a combination of toxicroak and mamo/crawdaunt to clean is usually my answer for them.)
Another weakness of this team is tight interdependence on others to cover weaknesses- this is like a monotype team I(particularly a steel one) in that once you break one link, it is very easy to exploit individual weaknesses in this team. I don't also particularly like stall matchups (who does) and a lack of a taunt user/designated stallbreaker does show (although the meta game has shifted away from stall IMO- and its an environment where big lobster does shine if you keep him status free.) A lack of a sweeper in the team does also limit it, but the lack of a single 'win con' is the team's ultimate strength- no one mon is more important than another in this team, which makes it truly terrifying when used appropriately.
Strengths:
Players using 'meta' picks like lando t, ash greninja, tapu koko, heatran, toxapex and kartana. Garchomp does badly, although I haven't seen him used for a wee while now. Essentially this team has an answer for virtually every mon in the tier and there aren't too many situations where there is an 'unwinnable matchup.' The team does well against the Tapus as a whole and isn't fazed by weather wars (gen 5 throwback.) nor does it get swept by common sweepers. This team won't suit everyone and does needs a trainer whose playstyle is fast-paced, likes pivots, and isn't afraid of making a bold read. Your ideal matchup is probably hyper offence (given how easily banded big lobster can clean late-game)
Feel free to let me know what yous think about this as a start to anti-meta teams (and if I have opened up a whole new can of worms then my day is complete XD)- I've also probably missed something in the team. Let me know if you want EV breakdowns as well but tbh only fck fairies has anything particularly non standard.
JoBH