I've gotten really good success with a general rain team. Leading with Politoed, Gastrodon, and Ludicolo with Thundurus, Kingdra, and M-Scizor in the back. All of their sets are pretty typical for a rain team with a few specific features.
Gastrodon is by far the most important member of the team. I run Sassy with 0 speed IVs and invested in Def and SpD with Assault Vest. With his speed he's almost always last anyways so I figured I'd go for something against Trick Room teams. Keeping him alive to make the most out of Storm Drain boosts is critical and I find he hits really hard with no investment into damage hence the stat allocation and item. Fake Out on Ludicolo and Encore on Politoed help keep him going even longer. If I predict a grass move I can swap in Scizor, otherwise I Muddy Water/ Scald if I'm against a Wide Guard user.
I want to replace something in the back with Toxicroak. If Gastrodon falls I find I have a hard time working around Surf hitting allies, so another absorber would be great. Healing 5/8 health per turn would be pretty solid, although I'm unsure just how bulky I can get him and still put out damage.
I've notice a lot of NA players run Dark Void Smeargle which is insanely annoying. A lot of them even run it with stuff like M-Kanga and Talonflame and any combination of Pokemon from the top 10 usage on Smogon. I can generally beat them unless I get very unlucky though. NA players also really like using Safeguard then Swaggering their own heavy hitter, but it's usually limited to QuakeEdge users which rain tends to walk all over.
JP players on the other hand all seem to use a similar core, especially as you get around the 2k mark. Cresselia, Hitmontop, and Heatran are on just about all the teams, and they are often the 3 that lead as well. Cresselia usually has Trick Room and Helping Hand, with Hitmontop running Fake Out and Wide Guard. It's not too bad to beat normally, but when they run Abomasnow in this set up I have huge issues with managinga win. My main answer to Abomasnow is M-Scizor, but I feel I need to put another answer in my team for it. The fact that it clears rain when it enters and when it Mega Evolves is very troublesome. Getting rain back up isn't a huge problem as I run a few Rain Dancers to beat CharY anyways, but I can still fall behind quick without M-Scizor.