Ludicolo

Swift Swim
Speed doubles in rain.
Rain Dish
Heals 1/16 max HP in rain.
Type Tier
Water / Grass BL
Statistics
Min- Min Max Max+
HP
80
- 301 364 -
Atk
70
158 176 239 262
Def
70
158 176 239 262
SpA
90
194 216 279 306
SpD
100
212 236 299 328
Spe
70
158 176 239 262
Name Item Ability Nature

Rain Support

Leftovers Swift Swim Calm
Moveset EVs
~ Rain Dance
~ Surf / Grass Knot
~ Ice Beam
~ Leech Seed
204 HP / 76 SpA / 124 SpD / 104 Spe

If you desire weather support, Ludicolo is a fine choice to provide it. He can scare off Hippowdon, hurt Tyranitar with his STAB moves (although switching in directly is risky) and sponge Abomasnow's Blizzard very well. Surf will help against Heracross and is boosted by the Rain, while Grass Knot lets you hurt other Waters.

The EV spread generates just enough Special Attack to guarantee a OHKO on minimum HP Salamence (who fails to OHKO with Choice Specs Draco Meteor), and just enough HP for the highest possible Leftovers threshold.

Name Item Ability Nature

Rain Offense

Leftovers / Damp Rock Swift Swim Modest
Moveset EVs
~ Rain Dance
~ Surf / Hydro Pump
~ Grass Knot
~ Ice Beam
152 HP / 252 SpA / 104 Spe

This is surprisingly dangerous if your opponent is not prepared for it. Surf is generally the preferred option for Water STAB, but Hydro Pump has a slim chance of OHKOing a Choice Scarf Heracross. Leftovers is recommended, but Damp Rock has its merits in a Rain themed team.

Name Item Ability Nature

Stall

Leftovers Swift Swim Calm
Moveset EVs
~ Leech Seed
~ Protect
~ Surf / Grass Knot
~ Toxic / Ice Beam
252 HP / 76 SpA / 180 SpD

Hit your enemies with Leech Seed and Protect to regain HP, while theirs is slowly drained. Either STAB move is useful. Surf hurts Steels like Skarmory and helps to wear down an incoming Heracross. Grass Knot does decent damage to Gyarados, in case he hits Ludicolo with Taunt. Toxic makes Ludicolo an even bigger pain, just beware of hitting Heracross with it, although you do have Protect to scout what it is planning to do next. Ice Beam hits other Grass-types, but it won't really threaten the likes of Celebi and Venusaur. Still, it never hurts to have something to batter Salamence with. This set works even better with support from Toxic Spikes.

Other Options

Seismic Toss gives you consistent damage against everything barring Ghosts, and helps against the likes of Calm Mind/Sub Raikou. Hidden Power Electric is an option if you really fear Gyarados, although Grass Knot already puts nice dent in him, ThunderPunch for those who cannot manipulate Hidden Power at will. Giga Drain and Energy Ball make alternative Grass attacks to Grass Knot, but in standard play most things you'd use them against are heavy enough to make Grass Knot worth it—think Tyranitar and Milotic—while things you wouldn't want to be stuck with Grass Knot against such as Porygon-Z and Azelf can be taken care of with Surf.

The Substitute/Leech Seed combination is another possibility, but is not well supported by poor initial Speed. Rest is a recovery option for Ludicolo and removes other status for all it's worth, you'll want to back it up with Aromatherapy or Ludicolo can become a liability.

Ludicolo can go physical (albeit off 70 base Attack), with Swords Dance, Waterfall, elemental punches and Razor Leaf, but Sceptile does it better. Fake Out is there if you want it (only realistically viable in 2 v 2 play). Rain Dish is rarely a better choice than Swift Swim.

EVs

202 speed should be a minimum on Rain Dance sets, so you can outrun Choice Scarf Heracross. You don't really need any more Speed than that, although bumping Ludicolo up to 222 to outrun Adamant Tyranitar isn't a bad idea. You can add a few more EVs to hit an initial Speed of 228, which outruns most Gliscor before you set up, and Choice Scarf Garchomp after Rain Dance is active.

76 Special Attack EVs lets you OHKO most Salamence. On all defensive sets, focus on HP is recommended before working on Special Defense. Without Leftovers, make Special Defense and HP as equal as possible (with the odd point in HP).

Opinion

Ludicolo is often an underrated Pokémon. It does an efficient job of handling Starmie and performs adequately against any Gyarados without Stone Edge. It can switch with ease into all other standard Water Pokémon, in particular Swampert, but beware of Milotic's Hypnosis. Overall, Ludicolo is a solid choice on most teams, capable of providing good support and even makes a surprisingly decent sweeper.

Counters

Without Surf, Heracross is switching into Ludicolo every time. Even with Surf, it is as good an opportunity as any. Toxicroak absorbs Surf and shrugs off Grass Knot, and is also immune to Toxic. Tentacruel takes Surf and Ice Beam like a pro, turns Leech Seed against you with Liquid Ooze, is immune to Toxic and can massacre Ludicolo with STABed Poison Jabs or Sludge Bombs. Celebi can stall Ludicolo and set up Calm Minds, and it nearly always survives two Ice Beams. He might eat a critical hit in the long run though. If Ludicolo leaves the house without Ice Beam, it is set-up fodder for Salamence and Dragonite. Blissey and Snorlax shrugs off his attacks, but both of them will hate Leech Seed.