BIG STALL PERSON.
Amoonguss is absolutely fantastic; the best Keldeo counter in the game, a phenomenal Breloom counter, can take on Venusaur in the rain, etc. Amoonguss is absolutely amazing, and should be played on any team lacking a defensive core. It covers so many threats at once, can run Shed Shell and not mind the recovery, etc. In addition, it is at least somewhat diverse in what moves it can choose.
Bliss/Chans are also amazing on stall, for 2 reasons generally. 1 is for Heal Bell, which eases the play of stall throughout the match should you play against a WoW user or get a crucial wall frozen. You can also run Rocks and not have to run a second steel type to overlap the coverage you get. Stall teams NEED all 6 slots, no exceptions. And of course, special walls and Wishpassing? Yes please.
Ferro is cool, not as cool as he was before with all the new threats running around, but he still can do his job fine. Leech Seed, hazards, TWave, good STABs, etc. make him an above average stall Poke. Forry is in the same boat, only it can ease prediction with Volt Switch, spin, and set up TSpikes, while exchanging Iron Barbs, TWave, Leech Seed, and a good STAB. Skarmory is another Steel Spiker, but this time it has access to a phazing move, immediate recovery, and a flying STAB, which is useful for threats like Terrakion.
Jellicent, Tentacruel, and Slowbro are the premier Bulky Waters of this gen. Jellicent is better for breaking other stall, Tentacruel is better for spinning (ya don't say) and laying down Toxic Spikes or messing up other stall Pokemon with the dreaded SubToxic set in the rain. Jellicent is notable for being able to beat some Manaphy 1 on 1, especially if it carries Hail. Slowbro is notable for Regenerator, and paired with other Regenerators such as Amoonguss, makes it amazing for Stall cores, and Slowbro + Amoonguss is a fantastic core alone, which is good for balance.
Tyranitar and Hippo are two Sand setters; the former is used for its much superior mixed coverage and special bulk, while the latter is used as a physical tank and phasing capabilities. Both have access to the ever useful Stealth Rock, which is mandatory on any stall team.
Gliscor and Heatran are a bit less common on purestall teams than others, but have amazing type coverage, and access to many annoying moves (SubTect for Gliscor, TormentTran for Heatran), and they both cover a large amount of threats.
The majority of the threats on the Stall threatlist can be handled much easier if Rainstall is being played. Blaziken's commonly sun boosted Flare Blitz is neutralized from the rain, making Tentacruel, Gliscor, Jellicent, and Slowbro hard counters to it, taking low damage and resisting its STABs. Chandelure takes literally nothing out of stall if you run Shed Shell, as all stall teams should have something to deal with it (Toxic Spikes + Chansey or Blissey, Tentacruel, Gastrodon, Heatran, or Tyranitar), and unless it is Sub Calm Mind without Tspikes down, you should be fine. Excadrill can be covered with Skarmory, Gliscor, and Hippowdon, although these can all have some difficulties depending on what sets Excadrill runs (Life Orb Adamant with Rock Slide, Air Balloon Adamant with Return, and Air Balloon Adamant with EQ) and hax. Keldeo is handily countered by Specially Defensive Amoonguss, Toxic Jellicent, and Toxic Tentacruel. Manaphy is a bit harder, Jellicent and Suicune with a super effective Hidden Power can handily counter Manaphy, but there are few stall Pokes that can reliably counter Manaphy. Under rain, Amoonguss, some Skarmory, and some Ferrothorn can take it in rain, but in sun it has few viable counters if it runs HP Fire. All of these are difficult but manageable to cover.
IMO rainstall is the way to go.
