One Pokemon that is often overlooked is the moon maiden Cresselia. She is among the bulkiest of ANY type of Pokemon, with stats obviously inclined towards walling. She's traditionally been forgotten in Singles because of her unreliable recovery move Moonlight, but Doubles sees her differently:
Cresselia #488
This set sees Cresselia taking an almost entirely supportive role. One of the enemies is too fast for your partner? Have him Protect while she slows them down. Physical attacks looking a little dangerous? Wall them. Crack a smile as what took your foe two turns to do is nullified by Moonlight. The Spe EVs should give Cresselia enough to outspeed base 130's after an Icy Wind, while the SpD investment guards against Ghost Gem Shadow Balls from Chandelure.
Helping Hand here is almost necessary because Cresselia often finds herself, after her partner Protects and she Icy Winds, having nothing to do. At the same time, said partner may not be able to OHKO one or two of the foes. Usually hard-hitters with only moderate speed (Like Chandelure) are chosen with this Cress, so with a Helping Hand and the right type matchup, at least one thing is going down.
This set suffers from Rain teams for three reasons: 1) Moonlight is nerfed, 2) Cresselia isn't resistant to any common rain-element types, and 3) without a slot for Sunny Day, Cresselia can't change the weather (and usually that's her job, since your other partner will need to be a sweeper if you want to get anything done).
A Cress meant to take advantage of Drought teams and cover its common weaknesses. Outside of Hidden Power, the Grass- and Fire-type abusers of Sun don't have much in the way of Ice-type attacks. Cress comes in with Ninetales, takes a Dragon- or Fire-type attack and ignores a Ground-type one, and Ice Beams the dragons straight to hell. With the sun in play, it's well possible to get full HP redemption after 2-3 turns of onslaught with Moonlight.
Helping Hand here is important because of the number of Heat Wave/Eruption-users that will no doubt see some use in a Drought Doubles team. Cress often finds herself unable to do anything with just Ice Beam, and the immensely prioritized Helping Hand fixes that. Cresselia will usually be the only support-type Pokemon on an offensive Drought team, so the move's usefulness won't be wasted. Calm Mind and Sunny Day compete for a spot here. Do you want to be able to boost yourself statistically during a turn you can't do anything else, or have insurance against the many slower weather-setters on Turn 1?
->Trick Room<-
Cresselia @ Mental Herb / Macho Brace / Sitrus Berry
SASSY
+Levitate+
252 HP / 6 Def / 252 SpD
-Trick Room
-Reflect / Light Screen
-Helping Hand
-Psychic
The bulkiest overall non-uber Trick Room user with the possible exception of Eviolite Dusclops. The especially high SpD guards against hard hitters like Ghost Gem Shadow Ball and Drizzle-boosted Hydro Pumps. Then Reflect and either assist your already super-strong Trick Room Pokemon like Hariyama and Marowak with Helping Hand or Ice Beam/Psychic to KO an already weak foe or provide general coverage.
Mental Herb is Cresselia's safety kit against Taunt (And, if a foe Whimsicott didn't Taunt already first turn, it stops a priority Encore second turn) while Macho Brace allows Cresselia to outspeed things it wouldn't normally be able to. Cress' bulks means outside of a crit almost nothing with OHKO it before Trick Room, so its biggest worry is Imprison, specifically from Chandelure, and Fake Out. Weavile can stop both of these, having an extremely fast Fake Out and being able to Fling a King's Rock on Ghosts, but is so fast it may not find any other use on a TR team. You can also delay trying to set up TR if you suspect Chandelure of using Imprison, and gang up on it, 2HKOing it if it has a sash.
The options of Sitrus Berry as an item and Light Screen and Psychic as moves are based off of the very potent "Standard 2010" Cresselia, which was paired often with Iron Ball, Fling Groudon.

Cresselia #488
HP: 120
Atk: 70
Def: 120
SpA: 75
SpD: 130
Spe: 85
Atk: 70
Def: 120
SpA: 75
SpD: 130
Spe: 85
PHP:
Level-Up Moves
-- Confusion
-- Double Team
Lv11 Safeguard
Lv20 Mist
Lv29 Aurora Beam
Lv38 Future Sight
Lv47 Slash
Lv57 Moonlight
Lv66 Psycho Cut
Lv75 Psycho Shift
Lv84 Lunar Dance
Lv93 Psychic
Machine Moves
TM03 Psyshock
TM04 Calm Mind
TM06 Toxic
TM10 Hidden Power
TM11 Sunny Day
TM13 Ice Beam
TM15 Hyper Beam
TM16 Light Screen
TM17 Protect
TM18 Rain Dance
TM19 Telekinesis
TM20 Safeguard
TM21 Frustration
TM22 SolarBeam
TM27 Return
TM29 Psychic
TM30 Shadow Ball
TM32 Double Team
TM33 Reflect
TM42 Facade
TM44 Rest
TM45 Attract
TM48 Round
TM53 Energy Ball
TM57 Charge Beam
TM68 Giga Impact
TM70 Flash
TM73 Thunder Wave
TM77 Psych Up
TM85 Dream Eater
TM86 Grass Knot
TM87 Swagger
TM90 Substitute
TM92 Trick Room
Gen IV Tutor Moves
(Pt/HG/SS) Fury Cutter
(Pt/HG/SS) Helping Hand
(Pt/HG/SS) Icy Wind
(Pt/HG/SS) Mud-Slap
(Pt/HG/SS) Signal Beam
(Pt/HG/SS) Snore
(Pt/HG/SS) Swift
(Pt/HG/SS) Trick
(Pt/HG/SS) Zen Headbutt
(HG/SS) Gravity
(HG/SS) Magic Coat
(HG/SS) Role Play
Cresselia -> Double Battles
->Support<-
Cresselia @ Light Clay
TIMID
+Levitate+
252 HP / 94 SpD / 164 Spe
-Icy Wind
-Reflect
-Helping Hand
-Moonlight
TIMID
+Levitate+
252 HP / 94 SpD / 164 Spe
-Icy Wind
-Reflect
-Helping Hand
-Moonlight
This set sees Cresselia taking an almost entirely supportive role. One of the enemies is too fast for your partner? Have him Protect while she slows them down. Physical attacks looking a little dangerous? Wall them. Crack a smile as what took your foe two turns to do is nullified by Moonlight. The Spe EVs should give Cresselia enough to outspeed base 130's after an Icy Wind, while the SpD investment guards against Ghost Gem Shadow Balls from Chandelure.
Helping Hand here is almost necessary because Cresselia often finds herself, after her partner Protects and she Icy Winds, having nothing to do. At the same time, said partner may not be able to OHKO one or two of the foes. Usually hard-hitters with only moderate speed (Like Chandelure) are chosen with this Cress, so with a Helping Hand and the right type matchup, at least one thing is going down.
This set suffers from Rain teams for three reasons: 1) Moonlight is nerfed, 2) Cresselia isn't resistant to any common rain-element types, and 3) without a slot for Sunny Day, Cresselia can't change the weather (and usually that's her job, since your other partner will need to be a sweeper if you want to get anything done).
->Drought<-
Cresselia @ Leftovers
BOLD
+Levitate+
252 HP / 252 Def / 6 SpD
-Psychic / Ice Beam
-Helping Hand
-Calm Mind / Sunny Day
-Moonlight
BOLD
+Levitate+
252 HP / 252 Def / 6 SpD
-Psychic / Ice Beam
-Helping Hand
-Calm Mind / Sunny Day
-Moonlight
A Cress meant to take advantage of Drought teams and cover its common weaknesses. Outside of Hidden Power, the Grass- and Fire-type abusers of Sun don't have much in the way of Ice-type attacks. Cress comes in with Ninetales, takes a Dragon- or Fire-type attack and ignores a Ground-type one, and Ice Beams the dragons straight to hell. With the sun in play, it's well possible to get full HP redemption after 2-3 turns of onslaught with Moonlight.
Helping Hand here is important because of the number of Heat Wave/Eruption-users that will no doubt see some use in a Drought Doubles team. Cress often finds herself unable to do anything with just Ice Beam, and the immensely prioritized Helping Hand fixes that. Cresselia will usually be the only support-type Pokemon on an offensive Drought team, so the move's usefulness won't be wasted. Calm Mind and Sunny Day compete for a spot here. Do you want to be able to boost yourself statistically during a turn you can't do anything else, or have insurance against the many slower weather-setters on Turn 1?
->Trick Room<-
Cresselia @ Mental Herb / Macho Brace / Sitrus Berry
SASSY
+Levitate+
252 HP / 6 Def / 252 SpD
-Trick Room
-Reflect / Light Screen
-Helping Hand
-Psychic
The bulkiest overall non-uber Trick Room user with the possible exception of Eviolite Dusclops. The especially high SpD guards against hard hitters like Ghost Gem Shadow Ball and Drizzle-boosted Hydro Pumps. Then Reflect and either assist your already super-strong Trick Room Pokemon like Hariyama and Marowak with Helping Hand or Ice Beam/Psychic to KO an already weak foe or provide general coverage.
Mental Herb is Cresselia's safety kit against Taunt (And, if a foe Whimsicott didn't Taunt already first turn, it stops a priority Encore second turn) while Macho Brace allows Cresselia to outspeed things it wouldn't normally be able to. Cress' bulks means outside of a crit almost nothing with OHKO it before Trick Room, so its biggest worry is Imprison, specifically from Chandelure, and Fake Out. Weavile can stop both of these, having an extremely fast Fake Out and being able to Fling a King's Rock on Ghosts, but is so fast it may not find any other use on a TR team. You can also delay trying to set up TR if you suspect Chandelure of using Imprison, and gang up on it, 2HKOing it if it has a sash.
The options of Sitrus Berry as an item and Light Screen and Psychic as moves are based off of the very potent "Standard 2010" Cresselia, which was paired often with Iron Ball, Fling Groudon.