This duck's goal is to stop all weather teams in their tracks. With its ability Cloud Nine, Golduck can achieve this while also providing valuable support to the rest of its team. Golduck has a decent base 85 Speed, and it can easily put this to good use with its access to Icy Wind. Its movepool is not the greatest, but Golduck's niche is not in attacking, it is in supporting.
Golduck is one of three Pokemon that get access to Cloud Nine. Of the 4 auto-weather Pokemon, Golduck has big problems with Abomasnow and Hidden Power Grass Politoed, but it checks weather pretty well otherwise. Since many teams in VGC 2012 rely heavily on setting up weather, Golduck is a real nuisance. Cloud Nine is a support ability, so it only makes sense that Golduck's moveset is supporting as well. It should be noted that Cloud Nine does not stop weather from occurring, it just negates any effects that would come from it while Golduck is on the field. Scald is usually preferred because of its chance to burn, as well as better accuracy than Hydro Pump. Icy Wind helps with coverage and slowing threats down. Focus Sash can't be broken by weather, so it's a great choice for Golduck. It also helps Golduck survive powerful boosted attacks, which is highly useful considering the prevalence of Gems in VGC. Protect is a given, as it is needed to preserve Focus Sash and to keep Golduck's Cloud Nine active as long as possible. The choice between Hidden Power Electric, Hidden Power Grass, and Encore can be complicated; it depends on how Golduck's teammates handle threats. Hidden Power Electric is mostly for Gyarados, but it also hits other common threats such as Rotom-W. Hidden Power Grass can be used if Golduck's teammates have problems with Gastrodon. Encore, is more of a surprise factor that works if Golduck does not need the coverage from the Hidden Powers.Team Options & Additional Comments >>>
In order to use Golduck and Shedinja together, Golduck would need a bulkier spread as Shedinja appreciates Focus Sash. The choice between Sitrus, Wacan, and Rindo depends on what kind of support the rest of the team needs; the choice is usually Wacan because of how common Thunderbolt is in VGC. Soak is also a gimmick that is usable with this pair, but it gets stopped by Gastrodon.
Golduck does have a few alternatives for its moveset. Like most Water-types, it gets access to Surf, but Surf also hits Golduck's partner, so Scald and Hydro Pump are preferred. Focus Blast is usable, but its poor accuracy and inferior coverage makes Icy Wind the better choice. Ice Beam can be used over Icy Wind for more power. Yawn and Hypnosis are both alternative surprise tactics, but neither work as well as Encore. Magic Coat is very situational and requires a high level of prediction. It helps against Pokemon that abuse Prankster, such as Thundurus and Sableye. Light Screen is another option, but unless Golduck's teammates desperately need a Special Defense boost, it should not be used.
Although it does not work as well as the support set, an offensive set with a Modest nature and a Water Gem could be used instead. Swift Swim is usable here, but Cloud Nine outclasses Swift Swim because of how disruptive it can be.
Checks and Counters
Golduck can easily be beaten by the common Thunderbolt and the slightly less common Hidden Power Grass; without Focus Sash intact, it is easily OHKOed by most Pokemon with these moves. Golduck also has trouble with threats that wall it, such as Rotom-W and Gyarados; the former can easily OHKO Golduck with STAB Thunderbolt as well. Thundurus, Zapdos, and Virizion all outspeed Golduck and OHKO it. Focus Sash is very important against these Pokemon, but it still takes several Icy Winds to KO them. Spread moves are the bane of Focus Sash, breaking it and allowing the opponent's partner to take care of Golduck. Golduck can't do much to Abomasnow without Focus Blast, while Abomasnow can 2HKO it. Politoed is normally on the bulkier side, so it would win one-on-one with Hidden Power Grass. Ferrothorn walls Golduck and handles it with a STAB Power Whip. Golduck can't do much to Scizor, Metagross, and Escavalier other than hope for a Scald burn. Pokemon with the ability Guts benefit from Scald, so Golduck tends to have a hard time with them.