It's been a while since I played any OU. I've been trying to learn the meta and I wanted to try an HO team with some of the new Swift Swim users. This is my best try at it and it got me to about 1350 (which isn't particularly impressive, but I'm pleased with it). I started with a core of 
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which I shamelessly stole from another RMT and added 
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to try to present a breadth of threats that puts pressure on the opponent to maintain a lot of different kinds of answers.
The Team
Pelipper @ Damp Rock
Ability: Drizzle
EVs: 248 HP / 252 Def / 8 SpD
Bold Nature
- Scald
- Roost
- U-turn
- Defog
There's not a whole lot to say about Pelipper in a rain team. We need a rain setter, actually spending a turn on Rain Dance seems like it's probably unforgivably slow for OU, and Pelipper has better typing and moveset than Politoed does. Defog is convenient given that we're usually about to rotate into one of our kinda flimsy offensive mons. U-turn can be used to get one of our offensive mons in without having to actually take a hit on the switch since shes fairly slow, but you need to be careful not to sac her early. One matchup of note is that scald actually does really good damage if they open with lando-t to set stealth rock.
Barraskewda @ Choice Band
Ability: Swift Swim
EVs: 252 Atk / 4 Def / 252 Spe
Adamant Nature
- Liquidation
- Close Combat
- Flip Turn
- Aqua Jet
Barraskewda feels like the reason to run rain in OU right now. Liquidation in the rain is an OHKO against so many things in the format and even against some of the things it doesn't OHKO a little chip damage is all it needs to sweep up. Close Combat is a nice mix-up against defensive steel types. Flip Turn lets you get some damage off especially if you predict a switch into a counter. Aqua Jet is honestly underperforming for me a bit. The priority is nice if you lost Pelipper for some reason, but I don't find myself using it very much so maybe that should be another coverage move.
Seismitoad @ Life Orb
Ability: Swift Swim
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
IVs: 0 Atk
- Stealth Rock
- Weather Ball
- Earth Power
- Focus Blast
Seismitoad is the special counterpart to Barraskewda's physical attacking set. Weather Ball in the rain and Earth Power are the main hard hitting go-tos and Focus Blast is good for coverage. Life Orb puts a bit of an expiration date on her, and as such Seismitoad is usually the mon I'm saccing early to wear down walls rather than saving to sweep up. The electric immunity is pretty important though, so you might have to play more conservatively on a team with lots of volt switch users. Seismitoad is also our Stealth Rock user, which I find myself not using very much. Given my tendency not to spend a turn on it that could possibly be another coverage move, but I think I probably should just be valuing Stealth Rock higher.
Zapdos @ Heavy-Duty Boots
Ability: Static
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Thunder
- Hurricane
- Weather Ball
- Roost
Zapdos is an excellent option for special coverage in a rain team. Thunder and Hurricane both hit incredibly hard with STAB and can't miss in the rain. Weather Ball is another nice coverage move especially if you predict a ground type switch in to blank a Thunder (in the rain). Unfortunately the miss chance on Thunder and Hurricane make her a lot less useful outside of rain (although do note that Weather Ball can be used in other weather), so I try to avoid having to use Zapdos outside of rain other than as a pivot or to get off a Roost. The Heavy-Duty Boots are pretty important, as without them Stealth Rock will very quickly wear down Zapdos, so try to avoid Knock Off.
Kartana @ Choice Scarf
Ability: Beast Boost
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Leaf Blade
- Knock Off
- Sacred Sword
- Smart Strike
Kartana is the first somewhat unconventional choice for a rain team. I went with a choice scarf set that gives us access to a nice spread of physical coverage that's gonna outspeed most of the format whether it's raining or not. Sacred Sword is nice against certain defensive walls, especially Bulk Up or Iron Defense users. Smart Strike is nice against defensive fairy types and makes this a good lead against a hail setting Ninetales-Alola. Knock off is a good option to get some value early especially when you expect a switch out. Beast Boost makes this another potential physical sweeper for us, especially if our opponent is a little banged up.
Clefable @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 196 Def / 60 Spe
Bold Nature
IVs: 0 Atk
- Calm Mind
- Moonblast
- Soft-Boiled
- Flamethrower
Clefable another potentially strange choice for a rain team. This is a fairly bulky Calm Mind set that gives us one of our only real pivots. Moonblast is a nice counter to dragon types, especially Dragapult, and Flamethrower gives us a nice way to wear down grass types or possibly certain steel types. Calm Mind and Soft-Boiled make Clefable a threat of its own, which is slow to set up but forces the opponent to eventually respond. Clefable is a good mon to tank a suspected Knock Off early on because she doesn't desperately need Leftovers anyway. Magic Guard also makes it a nice pokemon to tank a toxic or switch easily into hazards.
The Problems
We'll start with the general here and move to the specific.
The first general problem to me is that the team is highly reliant on out-speeding the opponent. Obviously we're built to be able to do that fairly consistently with two Swift Swim users and a Choice Scarf Kartana, but if the opponent has something that's just very fast or sets up Trick Room or Sticky Web or has access to priority then most of our team are glass cannons who can't afford to take a hit. I'm not entirely sure how to address this outside of "don't play rain", but it does seem like a spot that I get "checkmated" a lot.
Another general problem is that a lot of our special coverage is reliant on rain to function at all. Zapdos in particular is excellent in the rain, but unreliable without it (and without access to water type through Weather Ball). Again the answer here might just be "don't lose Pelipper" but I'm not sure if it's wise even on a rain team to have so much of the team rely on rain to be useful.
There's a couple specific problem pokemon of note as well
Rillaboom is a monster against almost our entire team. Grassy Glide with priority easily OHKO's our Swift Swimmers and does enough damage against everything else that it feels very hard to have a good switch into. It seems like keeping Zapdos alive is pretty critical to have a chance at beating it. Clefable can do a lot of damage to it with Flamethrower, but it can't switch into it because it'll just get 2HKO'd by Grassy Glide.
Rotom-W walls a lot of our team and wears them down with Pain Split and Volt Switch. Kartana can OHKO with Leaf Blade but risks tanking a volt switch on the switch in and taking potentially crippling damage. Outside of Kartana there's just nothing that clears it all too quickly unless Clefable gets off a couple Calm Minds.
The other team's barraskewda is just as fast and lethal as ours is and we don't have anything that can really tank a hit off it. My strategy thus far has been to win the speed tie coinflip, but it'd probably be good to have a better plan.
+ + which I shamelessly stole from another RMT and added + + to try to present a breadth of threats that puts pressure on the opponent to maintain a lot of different kinds of answers.The Team
Pelipper @ Damp Rock
Ability: Drizzle
EVs: 248 HP / 252 Def / 8 SpD
Bold Nature
- Scald
- Roost
- U-turn
- Defog
There's not a whole lot to say about Pelipper in a rain team. We need a rain setter, actually spending a turn on Rain Dance seems like it's probably unforgivably slow for OU, and Pelipper has better typing and moveset than Politoed does. Defog is convenient given that we're usually about to rotate into one of our kinda flimsy offensive mons. U-turn can be used to get one of our offensive mons in without having to actually take a hit on the switch since shes fairly slow, but you need to be careful not to sac her early. One matchup of note is that scald actually does really good damage if they open with lando-t to set stealth rock.
Barraskewda @ Choice Band
Ability: Swift Swim
EVs: 252 Atk / 4 Def / 252 Spe
Adamant Nature
- Liquidation
- Close Combat
- Flip Turn
- Aqua Jet
Barraskewda feels like the reason to run rain in OU right now. Liquidation in the rain is an OHKO against so many things in the format and even against some of the things it doesn't OHKO a little chip damage is all it needs to sweep up. Close Combat is a nice mix-up against defensive steel types. Flip Turn lets you get some damage off especially if you predict a switch into a counter. Aqua Jet is honestly underperforming for me a bit. The priority is nice if you lost Pelipper for some reason, but I don't find myself using it very much so maybe that should be another coverage move.
Seismitoad @ Life Orb
Ability: Swift Swim
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
IVs: 0 Atk
- Stealth Rock
- Weather Ball
- Earth Power
- Focus Blast
Seismitoad is the special counterpart to Barraskewda's physical attacking set. Weather Ball in the rain and Earth Power are the main hard hitting go-tos and Focus Blast is good for coverage. Life Orb puts a bit of an expiration date on her, and as such Seismitoad is usually the mon I'm saccing early to wear down walls rather than saving to sweep up. The electric immunity is pretty important though, so you might have to play more conservatively on a team with lots of volt switch users. Seismitoad is also our Stealth Rock user, which I find myself not using very much. Given my tendency not to spend a turn on it that could possibly be another coverage move, but I think I probably should just be valuing Stealth Rock higher.
Zapdos @ Heavy-Duty Boots
Ability: Static
EVs: 4 Def / 252 SpA / 252 Spe
Timid Nature
- Thunder
- Hurricane
- Weather Ball
- Roost
Zapdos is an excellent option for special coverage in a rain team. Thunder and Hurricane both hit incredibly hard with STAB and can't miss in the rain. Weather Ball is another nice coverage move especially if you predict a ground type switch in to blank a Thunder (in the rain). Unfortunately the miss chance on Thunder and Hurricane make her a lot less useful outside of rain (although do note that Weather Ball can be used in other weather), so I try to avoid having to use Zapdos outside of rain other than as a pivot or to get off a Roost. The Heavy-Duty Boots are pretty important, as without them Stealth Rock will very quickly wear down Zapdos, so try to avoid Knock Off.
Kartana @ Choice Scarf
Ability: Beast Boost
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Leaf Blade
- Knock Off
- Sacred Sword
- Smart Strike
Kartana is the first somewhat unconventional choice for a rain team. I went with a choice scarf set that gives us access to a nice spread of physical coverage that's gonna outspeed most of the format whether it's raining or not. Sacred Sword is nice against certain defensive walls, especially Bulk Up or Iron Defense users. Smart Strike is nice against defensive fairy types and makes this a good lead against a hail setting Ninetales-Alola. Knock off is a good option to get some value early especially when you expect a switch out. Beast Boost makes this another potential physical sweeper for us, especially if our opponent is a little banged up.
Clefable @ Leftovers
Ability: Magic Guard
EVs: 252 HP / 196 Def / 60 Spe
Bold Nature
IVs: 0 Atk
- Calm Mind
- Moonblast
- Soft-Boiled
- Flamethrower
Clefable another potentially strange choice for a rain team. This is a fairly bulky Calm Mind set that gives us one of our only real pivots. Moonblast is a nice counter to dragon types, especially Dragapult, and Flamethrower gives us a nice way to wear down grass types or possibly certain steel types. Calm Mind and Soft-Boiled make Clefable a threat of its own, which is slow to set up but forces the opponent to eventually respond. Clefable is a good mon to tank a suspected Knock Off early on because she doesn't desperately need Leftovers anyway. Magic Guard also makes it a nice pokemon to tank a toxic or switch easily into hazards.
The Problems
We'll start with the general here and move to the specific.
The first general problem to me is that the team is highly reliant on out-speeding the opponent. Obviously we're built to be able to do that fairly consistently with two Swift Swim users and a Choice Scarf Kartana, but if the opponent has something that's just very fast or sets up Trick Room or Sticky Web or has access to priority then most of our team are glass cannons who can't afford to take a hit. I'm not entirely sure how to address this outside of "don't play rain", but it does seem like a spot that I get "checkmated" a lot.
Another general problem is that a lot of our special coverage is reliant on rain to function at all. Zapdos in particular is excellent in the rain, but unreliable without it (and without access to water type through Weather Ball). Again the answer here might just be "don't lose Pelipper" but I'm not sure if it's wise even on a rain team to have so much of the team rely on rain to be useful.
There's a couple specific problem pokemon of note as well
Rillaboom is a monster against almost our entire team. Grassy Glide with priority easily OHKO's our Swift Swimmers and does enough damage against everything else that it feels very hard to have a good switch into. It seems like keeping Zapdos alive is pretty critical to have a chance at beating it. Clefable can do a lot of damage to it with Flamethrower, but it can't switch into it because it'll just get 2HKO'd by Grassy Glide.
Rotom-W walls a lot of our team and wears them down with Pain Split and Volt Switch. Kartana can OHKO with Leaf Blade but risks tanking a volt switch on the switch in and taking potentially crippling damage. Outside of Kartana there's just nothing that clears it all too quickly unless Clefable gets off a couple Calm Minds.
The other team's barraskewda is just as fast and lethal as ours is and we don't have anything that can really tank a hit off it. My strategy thus far has been to win the speed tie coinflip, but it'd probably be good to have a better plan.