Politoed description

Politoed, The Frog Pokémon. 

It gathers groups of others as their leader. Its cries make Poliwag obey. Whenever three or more of these get together, they sing in a loud voice that sounds like bellowing. The curled hair on its head proves its status as a king. It is said that the longer and curlier the hair, the more respect it earns from its peers.
Overview

Oh Politoed, you crazy pink-cheeked swirly-tummied little critter. The pain you have wrought the OU tier is immeasurable. You and your endless rain... and, obviously, that's all Politoed is used for. Nobody sits there thinking "hm... I really need a bulky Water... Water Absorb Politoed, of course!". Basically, Politoed exists for Drizzle and Drizzle alone. Not saying it can't be useful outside of infinite rain, but it's the reason everyone adds it to their team. It can use Hypnosis... that's nice. Strong Water attacks, which is awesome. A fairly good support movepool? Great! But it's Drizzle we all go there for, and it's all we want out of the poor little green toad, whose ability is more desired than its own existence.

Abilities
Water Absorb: a great ability, normally. Absorb any Water attacks that touch you, giving you extra recovery and the perfect switch in to strong Water types.
Damp: less useful, but it could be worse. Stops Explosion and Selfdestruct being used.
Drizzle: the ability that has shaped 5th gen OU to forever be a weather fest. Infinite rain, supporting Steels, Swift Swimmers, Dry Skin Pokémon, Rain Dish Pokémon, Electric Pokémon, and Water Pokémon in general. Basically, this ability is incredible, and has taken infinite rain out of ubers and brought it into the main battling tier.
Drizzle me this, Batman!
- Hydro Pump / Surf
- Ice Beam
- Focus Blast
- Hidden Power [Grass] / Hidden Power [Electric] / Hypnosis
Item Attached: Choice Specs / Choice Scarf
Ability: Drizzle
EVs and Nature:
EVs: 4 HP / 252 SAtk / 252 Spd
Modest Nature (+SAtk, -Atk) / Timid Nature (+Spd, -Atk)
Outside of Belly Drum, this is Politoed's hardest hitting set. It can even OHKO Tyranitar with Hydro Pump, which is perfect considering you'd be fighting for weather superiority.Surf is more reliable, but I like Hydro Pump more personally. Ice Beam is the perfect move to combine with your Water attacks for coverage. Focus Blast breaks through Ferrothorn and other Steels like Empoleon. Hidden Power [Grass] hits Swampert and other Water/Grounds harder, but Hidden Power [Electric] hits Gyarados much harder than any other move. Hypnosis works best with Choice Scarf, so you can get a quick sleep then retreat.
Double status toad
- Scald
- Encore / Ice Beam
- Toxic / Hypnosis
- Protect / Substitute / Rest
Item Attached: Leftovers
Ability: Drizzle
EVs and Nature:
EVs: 252 HP / 4 SAtk / 252 SDef
Calm Nature (+SDef, -Atk)
A more defensive Politoed, used more as a status inflicter and standard bulky Water than the other sets. Scald is the best Water attack Politoed has access to, as it can inflict burn. Encore is amazing, and if you hit the opponent with it when they use Stealth Rock or what not, you get a free switch effectively. Ice Beam provides awesomely useful coverage. Toxic or Hypnosis depends on what you want for your main status. Protect stalls Leftovers and Toxic damage, whereas Substitute does this but protects you for more than one turn. Rest provides you with recovery.
Here comes the drum
- Belly Drum
- Waterfall
- Earthquake
- Return
Item Attached: Leftovers
Ability: Drizzle
EVs and Nature:
EVs: 4 HP / 252 Atk / 252 Spd
Jolly Nature (+Spd, -SAtk)
It's all about the Belly Drum. Belly Drum gives you +6 attack, meaning you deal a lot of insane damage. Waterfall is your main move here, doing the most damage due to STAB and rain. Earthquake is like... the best physical attack ever, and I'm really surprised Politoed has access to. Return combos amazingly with Waterfall, and is a nice, strong, reliable attack regardless.
EVs & Natures
Drizzle me this, Batman!
You could run way less Speed, enough to be below Tyranitar so your weather gets set up. I don't recommend this, but it's an option. Dropping Speed and adding to HP is an option regardless.
Double status toad
You could go for 252 Defence, maybe some Speed, but I think focusing on Politoed's strongest stats is probably the best idea, considering you're using it only for Drizzle.
Here comes the drum
Making Politoed bulky is a possibility, as you could survive more attacks once your HP drops. However, that sort of makes Belly Drum pointless if you aren't going all out.
Other Options
Body Slam, Counter, Endeavor, Haze, Hyper Voice, Perish Song, Psychic, Sleep Talk, Salac Berry
Body Slam is an option on the Belly Drum set, as it can paralyse, and is still fairly strong.
Counter is cool and all, but I'd rather use it on something that can definitely survive a physical hit. You could run Bold with max Defence, but that's about it.
Endeavor is... another option. You don't have any priority to really do much from it, sadly.
Haze gets rid of stat boosts.
Hyper Voice is a Normal special move that makes the cool Water/Normal combo.
Perish Song forces switches or kills the opponent's Pokémon outright. It's awesome. Especially if you combine it with a team of trappers.
Psychic is another special move worth consideration.
Sleep Talk comes with Dream World Politoed, which allows you to use a ResTalk set in combination with Drizzle.
Salac Berry is an option on the Belly Drum set with Substitute, as it allows you to go for a big sweep.
Double & Triple Battle Options
Drizzle makes it a great Pokémon to use. It means you can build your entire strategy around rain, without having to waste a moveslot for Rain Dance. It also uses Surf, which is always a great move in multiple Pokémon battles. Being pure Water is useful too, as it resists Surf and Blizzard. If, for some reason, you're using Politoed without Drizzle, you can make use of its other two abilities, both of which are useful in doubles and triples.
Partners
STOP FERROTHORN AT ALL COSTS. Ferrothorn is the be all and end all of rain teams, and walls them come hell or high water. Running something that uses strong Fighting attacks is a good idea, as running Fire moves in rain is pretty backwards. Honestly, Ferrothorn is the number one target to remove. Other targets to remove are Jellicent, Gyarados, bulky Waters, bulky Grass Pokémon, there's a few types that do well against rain teams. Aside from stopping Pokémon that might end you, pile the rest of your team with Pokémon that love the rain. Swift Swimmers, Hydration Pokémon, Dry Skin users like Parasect and Toxicroak, Steel types to lose the Fire weakness, there's honestly a huge amount of variety. Kabutops, Ludicolo, Vaporeon, Jirachi, it's practically endless. Zapdos is always a good choice to abuse 100% accuracy with Thunder.
Countering Politoed
It's a standard Water type with a few tricks up its sleeve. Cute images of a Politoed in a tuxedo have just swamped my brain. Anyway, it has a few special moves likeHypnosis and Encore that can mess you up, but otherwise it's a generic Water type. Ferrothorn, Jellicent, Gyarados, the standard switch ins work great. Bulky Grass Pokémon work well too, just avoid Ice Beam. To deal with Drizzle which, let's be honest, is a lot more threatening than Politoed alone, you have a number of ways. Firstly, your own weather. Tyranitar, Hippowdon, Ninetales, or Abomasnow. They all replace rain with sandstorm, sunny day or hail, but except for Abomasnow, they all lose and cannot switch into Politoed safely. There's also Cloud Nine and Air Lock, both of which stop all weather effects, although they are held by lacklustre Pokémon such as Altaria, Golduck and Lickilicky. You can also revenge kill the toad with Zapdos, Serperior, the list is huge, so I won't go on. As I've said, Politoed is a Water Pokémon with one or two tricks up its sleeve. All it has going for it is Drizzle and a few status moves... and a pretty cute design.

Locations in Games
Ruby/Sapphire/Emerald:
Trade from FRLG .
FireRed/LeafGreen:
Evolve Poliwhirl.
Colosseum/XD:
Trade from FRLG
Diamond/Pearl/Platinum:
Evolve Poliwhirl
HeartGold/SoulSilver:
Evolve Poliwhirl
Black/White:
Route 6