As others did it already, I will point some interesting Ability Combos.Unnamed (Call it Ability Alphabet for now. Alternate name might be Ability Merge)
Metagame premise: Every ability gets the effect of the next one, in an alphabetical order, added/merged to them (Moody is skipped for obvious reasons).
For an example, let's take a look at Serene Grace. The next ability is Shadow Shield. So as of now,Serene Grace's effects are: "This Pokemon's moves have their secondary effect chance doubled and if this Pokemon is at full HP, damage taken from attacks is halved".
The really OP abilities that would be banworthy otherwise don't really create threats. Huge Power is merged with Honey Gather, so the new users are things like Combee and Teddiursa. Pure Power adds it effect to Psychic Surge, so the only new user is Tapu Lele. Comatose goes to Kecleon. Adaptability is Zan Mode Darmanitan's new toy. Shadow Tag's effect is added to Shadow Shield, so the only new user would be Lunala, which is banned. Parental Bond is added to Own Tempo. Wonder Guard is given to... Wimpod out of all things. The only banworthy is Simple, which goes to Minior; and Protean Necrozma
The list bellow is uncomplete as of now.
Potential bans and threats:Adaptability: Vanilla Effects + If this Pokemon is KOed with a contact move, that move's user loses 1/4 its max HP
Aftermath: Vanilla Effects + This Pokemon's Normal-type moves become Flying type and have 1.2x power.
Aerilate: Vanilla Effects + While this Pokemon is active, the effects of weather conditions are disabled.
Air Lock: Vanilla Effects + This Pokemon's attacks have 1.3x power if it is the last to move in a turn.
Analytic: Vanilla Effects + If this Pokemon (not its substitute) takes a critical hit, its Attack is raised 12 stages.
Anger Point: Vanilllla Effects + On switch-in, this Pokemon shudders if any foe has a supereffective or OHKO move.
Bans: Battle Bond (Gets Beast Boost's effects added to itself), Volcanion (Water Absorb has now also the effects of Water Bubble), OU Banlist
Possible Bans: Minior (Simple Shell Smash), Wonder Guard (Merges with Wonder Skin, making Shedinja harder to hit with Seeds, WoWs and Toxics), Necrozma (Gets Protean)
Threats: Lucario (Steadfast merges with Steelworker), Gogoat (Grass Pelt merges now with Grassy Surge)
Questions for the community:
- Is Necrozma banworthy, since Prism Armor now has the effects of Protean added to it?
- Is Minior banworthy? It has Simple Shell Smash but not that good stats (I'd go with yes)
Torrent + Tough Claws: Feraligatr and Swampert can hit harder with Waterfall and Ice Punch now. And maybe Samurott might also benefit this.
Gooey + Grass Pelt: Not truly faithful, as you need to set up a Grass Terrain first and Goodra cannot use it. But once you did with Gogoat or Tapu Bulu, you had now fixed its bad Defense as long as Grass Terrain remains.
Damp + Dancer: Sound situational, but will help if you wanna deal with Quiver Dancers. I would still prefer Torrent Swampert though.
Dazzling + Defeatist: Bruxish is more useless now.
Delta Stream + Desolate Land: I know that Mega Rayquaza is Anything Goes only, but now it is very vulnerable to Ice-type again.
Disguise + Download: Mimikyu may get a free Attack in addition of Sword Dance. Stay the same otherwise.
Drought + Dry Skin: While lack of Water-type weakness is cool, taking damage gradually is not. Mega Charizard Y may not be attracted too much anyway.
Electric Surge + Emergency Exit: Tapu Koko says hello! Now he say goodbye after you drop it into half HP.
Fairy Aura + Filter: Xerneas is a bit more broken now...
Full Metal Body + Fur Coat: Solgaleo can resist to many contact moves now.
Gale Wings + Galvanize: Talonflame could use this to get rid of opposing Flying-type and Water-type.
Illuminate + Illusion: This will make a good way to induce paranoia when using Starmie, Lanturn or Shiinotic.
Intimidate + Iron Barbs: Discourage the Physical opponents even more.
Immunity + Imposter: Snorlax's high HP might give it an insane advantage in revenge killing.
Long Reach + Magic Bounce: If only Decidueye had Long Reach released... It could laugh off against Taunt and Toxic.
Mold Breaker + Moody: Banworthy? Quick banning Mega Gyarados is rather honest since Moody is a banned Ability in OU.
Own Tempo + Parental Bond: Almost anyone with this Ability can break subs, Disguise and Sturdy, so it's saying a lot.
Strong Jaw + Sturdy: Convenient for Revenge Killing, long as there is no entry hazards.
Volt Absorb + Water Absorb: Two immunities in one Ability? Well heck yes! Especially considering that Torrent is combined with Tough Claws.
Water Bubble + Water Compaction: Aquaranid can become a pain in the neck against Physical Water opponents.
Water Absorb + Water Bubble: Volcanion would be broken, yes, but did you take account for Quagsire, Lapras, Poliwrath + Politoed and even Mantine? At least Cacturne and Maractus will enjoy the Fire-type damage reducement.