Ninetales
Item: Leftovers
Ability: Drought
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Calm Nature
Nasty Plot
Flamethrower
Hidden Power Ice
Will-O-Wisp/ Hypnosis
There is no need for a Gem on Ninetales. Nasty plot is enough of a boost and you should rather consider a long term item like Leftovers on your weather Pokemon rather than a once use item. Solarbeam is something that I don't like. A lot of Ninetales I've seen run it, and all it takes is one Politoed switch in and Solarbeam now takes 2 turns, which means your opponent can now use Protect or switch to a grass/ poison type to take the hit.
You want a sweeper, right? Then invest EVs in its speed. If you use your Ninetales as a sweeper, rather than have it defensive, you need to look at the rest of your team and think about how it will work in the (likely) event that your Ninetale faints. Can your team continue functioning without your weather lead.
Gastrodon
Ability: Storm Drain
Item: Leftovers
EVs: 252 HP, 252 Sp. Def, 4 Sp. Atk
Nature: Sassy/ Calm
Scald
Earth Power
Recover
Toxic
Thunderbolt will OHKO Gyarados. Most rain sweepers, namely Thundurus-T, will be scarfed. A Scarfed Thundurus-T with 252 Speed EVs will outspeed your Gyarados after 1 Dragon Dance. You might as well go with Gastrodon for a rain counter, since it has Storm Drain, Recover, and Ground typing (which will help against other sun teams and Electric immunity).
Gliscor
Item: Toxic Orb
Ability: Toxic Heal
EVs: 252 HP, 180 Def, 76 Speed
Nature: Impish
- Swords Dance
- Earthquake
- Ice Fang/ Facade
- Protect/ Roost
Might as well give your sweeper some bulk. If you have Earthquake, there is no need for Brick Break; anything carrying a balloon can be dealt with by Ice Fang/ Facade, and then Earthquake, which gives powerful STAB.
Sableye
Ability: Prankster
Item: Leftovers
EVs: 252 HP, 128 Def, 128 Sp. Def
Nature: Calm
Will-O-Wisp
Recover
Taunt
Foul Play/ Night Shade
Leftovers > Focus Sash. Sableye will be able to use Recover with prankster anyway. You could also run a Trick set (using Iron Ball/ Sticky Barb/ Choice item) to ruin your opponent's cleric.
Kyurem-B
Item: Life Orb/ Choice Scarf
Ability: Teravolt
EVs: 200 Speed, 200 Sp. Atk, 108 Atk
Nature: Lonely
IVs: 30 Atk / 30 SAtk
Ice Beam
Outrage
Fusion Bolt
Dragon Claw
Freeze shock/ burn are useless moves. You use your Power Herb once and then you're left with something useless taking up a space in your moveset. Ice Beam does more damage over 2 turns, and has 100% accuracy.
The really good thing about Kyurem is that it can serve as a mixed sweeper; with 170 Atk and 120 Sp. Atk, it can use Ice Beam (as most ice moves are special) along with Outrage. Now that it's in OU, Dragonite is finished.
Jirachi
Ability: Seren Grace
Item: Leftovers
EV: 252 HP, 252 Sp. def, 4 Speed
Nature: Careful
Thunder Wave/ Body Slam
Iron Head
Wish
Protect/ Stealth Rock
Jirachi should abuse Serene Grace to its fullest extent. This set is genuinely annoying. Body Slam to deal damage (with 60% paralysis) or Thunder Wave for 100% paralysis. Your choice.
Mew @ Leftovers
Ability: Synchronise
EVs: 4 HP, 252 Sp. Atk, 252 Speed
Nature: Timid
Nasty Plot
Psychic
Shadow Ball
Flamethrower/ Aura Sphere
Okay, why is Mew holding a Big Root when it has no draining moves? Did you check what the item did before you gave it to Mew?
Since you had a sweeper set, go with this for Mew; standard Smogon set.
Thundurus-T
Ability: Volt Absorb
Item: Life Orb/ Choice Scarf
EVs: 252 Sp. Atk, 252 Speed, 4 HP
Nature:
Thunderbolt
Volt Switch
Hidden Power Ice
Grass Knot/ Focus Blast
Consider this to be the better Rain counter, due to Volt Absorb and STAB in Thunderbolt. Don't go with Thunder because it's 50% in Sun, so you'd have wasted a move if you are not facing a rain team. It will also provide coverage against grass types with HP Ice.
Venusuar
Item: Life Orb
Ability: Chlorophyll
EVs: 4 HP, 252 Sp. Atk, 252 Speed
Nature: Modest
Growth
Giga Drain
Sludge bomb
Sleep powder
Since you thought about Venusuar, here's a moveset for it. I'd go with Giga Drain over Solarbeam, because in rain it will do half the damage it usually does.
I know there are 9 Pokemon here, but I gave a set for all of them so you can choose for yourself what is best.
