Super Doubles Win Steak: 89
Item: Choice Specs
EVs: 252 SpA / 4 SpD / 252 Spe
Lv50 Stats: 165 78 95 156 121 122
- Hydro Pump
- Ice Beam
- Focus Blast
Gets the rain going and spam absurdly powerful Surfs. Ice Beam handles dragons and grass types, while Hydro Pump and Focus Blast have situational uses. Solid natural bulk, even without investment, allows her to survive a surprising amount of attacks.
Item: Black Sludge
Ability: Dry Skin
EVs: 4 HP / 252 Atk / 252 Spe
Lv50 Stats: 159 173 85 95 85 137
- Fake Out
- Drain Punch
- Sucker Punch
Fantastic leading partner with Politoed. Fake Out + rain boosted Surf is usually enough to KO threats; if not, Sucker Punch finishes them off. Between healings from Dry Skin, Black Sludge, and Drain Punch, Toxicroak can go from a sliver of health back to almost full within the span of a single turn. Protect is useful for avoiding obvious psychic/flying/ground attacks, providing a bit of extra healing, and scouting. I have considered changing Toxicroak's item to something that boosts his damage (thinking Muscle Band, a plate, or a gem) since Black Sludge healing is not always all that helpful.
*Random note about Dry Skin: seeing as Politoed resists water, CPUs love to repeatedly spam water attacks at Toxicroak despite his immunity
Item: Life Orb
Ability: Swift Swim
EVs: 48 HP / 252 SpA / 208 Spe
Lv50 Stats: 151 61 145 182 90 101
- Ice Beam
- HP: Grass
- Shell Smash
Omastar is a solid backup for Politoed, providing comparable damage output while boasting higher speed under rain and freedom of move choice. HP: Grass is fantastic for smashing those annoying Water/Grounds, namely Gastrodon and Quagsire. 208 speed EVs put Omastar at 202 speed in the rain or out of rain with a Shell Smash, allowing him to outspeed scarfSkarm and everything slower. I've debated moving the HP EVs to speed so Omastar can outspeed a few more things in the rain w/o a Shell Smash, though. Getting a Shell Smash in almost guarantees a win, so...
Ability: Dry Skin
EVs: 252 HP / 160 Def / 96 SpD
Lv50 Stats: 167 115 120 72 123 50
- Rage Powder
Parasect provides fantastic support not only to Omastar, but to the entire team. Rage Powder is the key, allowing Omastar to Smash or Politoed and Toxicroak to spam powerful attacks. Parasect's typing meshes extremely well with Omastar and Politoed - she resists the grass, electric, ground, and fighting attacks aimed at them, making prediction easy. Conversely, Protect saves her from obvious fire, flying, and poison attacks, as well as giving her some free healing. A second Dry Skin user is fantastic in the event that Toxicroak goes down early, allowing Politoed and Omastar to use Surf without fear. Spore proves useful as well, shutting down mons that aren't immediately threatening but can set up. X-Scissor is solid STAB that has the benefit of hitting psychic types that plague Toxicroak super-effectively.
Overall, this team is a lot of fun to play with. It took quite a while to learn its weakness and it underwent many tweaks along the way. The two leads have remained constant, but I've tried Dragonite (Hurricane/Thunder abuse), Virizion, Weavile, SB Sharpedo, and LO Starmie in the wings. Despite many changes, this team isn't perfect: teams packing an opposing weather starter can be a little rough. Those with multiple either fast or bulky electric/grass types can be problematic as well, though it depends largely on the other team members as well as their lineup order. Legendary teams leading with two major threats at once (Zapdos, Thundurus, Raikou, etc) have ended many streaks.
Picture for proof: http://imageshack.us/photo/my-images/856/img0020nr.jpg/