I've been following you for a while, but I've never posted before, so I take this chance to greet everybody. I had quite some experience with competitive battling, back when 2nd gen was new and fresh. I didn't play since then, I just started less than a month ago, and since I'm quite busy right now I didn't have much time to play.. I still lack experience with 3rd and 4th pokemons, which I never played (neither with the DS).
Now that we're done with the presentations, let's talk of the team.. I didn't came up with some cool name or story because I really don't have the time to do it, just wanted some counsel. Here's the team, hope you'll find it worthy and interesting :) :
Thundurus @ Shell Bell
Trait: Prankster
EVs: 4HP / 252 SAtk / 252 Spd
Modest Nature ( +SAtk, -Atk)
Volt Switch
Hidden Power [Ice]
Taunt
Thunder Wave
Tentacruel (M) @ Black Sludge
Trait: Rain Dish
EVs: 252 Hp / 4 SAtk / 252 SDef
Calm Nature ( -Atk, +SDef)
Scald
Toxic Spikes
Rapid Spin
Rest
Yes, I know, Rest. Many laugh at me whenever they see it, but most do not laugh anymore at the end of the battle.
With Black Sludge, Rain Dish (and often with Leech Seed set up before the switch by Ferrothorn) he can heal himself about 1/4 his HPs every turn (assuming the opponent pokemon has a similar amount of HPs) he can stall almost any special sweeper, even with Thunder. With leech seed (or with a scald on the switch) he can easily stall even Gengars with Thunder, 2HKOing them with Scald and eating 2 to 3 Thunders.
Rest allows him to completely heal after a supereffective special sweeper or to stall other pokemon that rely on Will-o-wisp or that try to cripple my with TWave/Stun Spore. In addition, more than once I found myself with only Tentacruel left against 3 or 4 Pokemons. If I managed to defeat all possible counters (fast/resistent to water physical sweepers, any pokemon with psyshock or any STABed Thunder or Psychic that can kill me with their side effects) 99% of the time I win: Toxic Spikes, Scald, Rest, Toxic Spikes, Rest, Scald, Rest and so on. For bulky water / special walls the plan is to burn them with scald or poison them with spikes, and waiting for them to die. If there's a pokemon that can heal his burn or switched in before the spikes.... Then, well, before I end all Rapid Spin + Rest PP (let alone toxic spikes) I can force 2 to 3 pokemon to Struggle and kill themselves with the recoil.
My only doubt is between Rain Dish and Liquid Ooze... against rain team rain dish is useful, but more than once I had myself wishing the opportunity to switch in tentacruel on a Drain Punch/Giga Drain which would have killed the opponent. Don't know what to do.
Ferrothorn (F) @ Leftovers
Trait: Iron Barbs
EVs: 252 Hp / 4 Atk / 252 Def
Impish Nature ( +Def, -SAtk)
Power Whip
Leech Seed
Stealth Rocks
Thunder Wave
Standard Physical Wall Ferrothorn set. I found her incredibly complementary to Tentacruel. Almost everything she can't take, Tentacruel will. And viceversa. Notably exceptions are powerful Earthquakes and Physical Fighters, both of which can handled by Gliscor.
The only true weakness that came to my mind are very powerful Fire physical attacks: Ferrothorn's obvious bane, Tentacruel frail Def often allow them to 2HKO Tentacruel, which forces me to very good prediction or to sacrifice someone in order to allow Tentacruel to enter without taking a hit on the switch.
Power Whip is often underrated and also hurts very very bad waters, grounds, rocks and those poor Espeons that switch in predicting a TWave/LSeed or Stealth Rocks. With a crit it's even a OHKO.
Gliscor (F) @ Toxic Orb
Trait: Poison Heal
EVs: 160 Hp / 96 Def / 252 Spd
Adamant Nature ( +Atk, -SAtk)
Ice Fang
Facade
Earthquake
Swords Dance
My first sweeper and another standard set. Enter against a weak pokemon and Quiver Dance. Many pokemon are already doomed. And Supereffective Special Sweepers are one of the biggest mistakes opponents do. With one Quiver Dance he outspeed almost everything, even some Deoxys-S if I remember well. Couple it with another Quiver Dance and he have already doubled his Special Defense (which has a very good 105 base). You can throw any special attack you won't, no chance you will OHKO him, not even with a crit. And from there, the opponent is in a loooooot of trouble.
Another classic sweeper with another standard set. Being bulky and having Mach Punch he can ignore speed evs, but having 1 additional point often gives me the edge against other Conkeldurr... being able to Drain Punch before the other Conkeldurr can be the difference between a W and a L sometimes. Just find a chance to set up and then kill everything everything that breaths.
Team Strategy:
Simple. Start with Thundurus and mess up with opponent's lead. Volt switch and put a counter in the field. Then use Tentacruel, Ferrothorn and Gliscor to cripple, annoy and weaken anything that the other guy throws at me until I can predict something good or he makes a mistakes and gives me a chance to set up Quiver Dance or Bulk Up. When one of my sweepers is ready to go then everything is a lot easier. Stop.
In the past I often used complex strategies with baton passers, annoyers and more recently with a sand team. But I found that no matter how new or how cool your strategy is, it will always soon come a time when dozens of way to cripple you start to pop out from everywhere. And there you must build anything from scratch. This time I'm trying to use something that relies on my skill (which must constantly improve, obviously) more than in some strange tactic.
Thanks everyone in advance for your counsel :)
Now that we're done with the presentations, let's talk of the team.. I didn't came up with some cool name or story because I really don't have the time to do it, just wanted some counsel. Here's the team, hope you'll find it worthy and interesting :) :

Thundurus @ Shell Bell
Trait: Prankster
EVs: 4HP / 252 SAtk / 252 Spd
Modest Nature ( +SAtk, -Atk)
Volt Switch
Hidden Power [Ice]
Taunt
Thunder Wave
As a lead, it's primary job is to either Taunt the opponent to prevent entry hazards or any setup or to scout with volt switch, based on the opponent's first pokemon.
Prankster TWave + Taunt allows me to stop setup sweepers, especially Shell Smashers: if they are going to Baton Pass --> Taunt, otherwise TWave. Most of the time it allows me to cripple the opponent after the first Shell Smash, and with good prediction I can also prevent the first one.
Hidden Power Ice is for Gliscors, Dragons and Grounds.
My biggest doubt is about the item...
Prankster TWave + Taunt allows me to stop setup sweepers, especially Shell Smashers: if they are going to Baton Pass --> Taunt, otherwise TWave. Most of the time it allows me to cripple the opponent after the first Shell Smash, and with good prediction I can also prevent the first one.
Hidden Power Ice is for Gliscors, Dragons and Grounds.
My biggest doubt is about the item...

Tentacruel (M) @ Black Sludge
Trait: Rain Dish
EVs: 252 Hp / 4 SAtk / 252 SDef
Calm Nature ( -Atk, +SDef)
Scald
Toxic Spikes
Rapid Spin
Rest
Yes, I know, Rest. Many laugh at me whenever they see it, but most do not laugh anymore at the end of the battle.
With Black Sludge, Rain Dish (and often with Leech Seed set up before the switch by Ferrothorn) he can heal himself about 1/4 his HPs every turn (assuming the opponent pokemon has a similar amount of HPs) he can stall almost any special sweeper, even with Thunder. With leech seed (or with a scald on the switch) he can easily stall even Gengars with Thunder, 2HKOing them with Scald and eating 2 to 3 Thunders.
Rest allows him to completely heal after a supereffective special sweeper or to stall other pokemon that rely on Will-o-wisp or that try to cripple my with TWave/Stun Spore. In addition, more than once I found myself with only Tentacruel left against 3 or 4 Pokemons. If I managed to defeat all possible counters (fast/resistent to water physical sweepers, any pokemon with psyshock or any STABed Thunder or Psychic that can kill me with their side effects) 99% of the time I win: Toxic Spikes, Scald, Rest, Toxic Spikes, Rest, Scald, Rest and so on. For bulky water / special walls the plan is to burn them with scald or poison them with spikes, and waiting for them to die. If there's a pokemon that can heal his burn or switched in before the spikes.... Then, well, before I end all Rapid Spin + Rest PP (let alone toxic spikes) I can force 2 to 3 pokemon to Struggle and kill themselves with the recoil.
My only doubt is between Rain Dish and Liquid Ooze... against rain team rain dish is useful, but more than once I had myself wishing the opportunity to switch in tentacruel on a Drain Punch/Giga Drain which would have killed the opponent. Don't know what to do.

Ferrothorn (F) @ Leftovers
Trait: Iron Barbs
EVs: 252 Hp / 4 Atk / 252 Def
Impish Nature ( +Def, -SAtk)
Power Whip
Leech Seed
Stealth Rocks
Thunder Wave
Standard Physical Wall Ferrothorn set. I found her incredibly complementary to Tentacruel. Almost everything she can't take, Tentacruel will. And viceversa. Notably exceptions are powerful Earthquakes and Physical Fighters, both of which can handled by Gliscor.
The only true weakness that came to my mind are very powerful Fire physical attacks: Ferrothorn's obvious bane, Tentacruel frail Def often allow them to 2HKO Tentacruel, which forces me to very good prediction or to sacrifice someone in order to allow Tentacruel to enter without taking a hit on the switch.
Power Whip is often underrated and also hurts very very bad waters, grounds, rocks and those poor Espeons that switch in predicting a TWave/LSeed or Stealth Rocks. With a crit it's even a OHKO.

Gliscor (F) @ Toxic Orb
Trait: Poison Heal
EVs: 160 Hp / 96 Def / 252 Spd
Adamant Nature ( +Atk, -SAtk)
Ice Fang
Facade
Earthquake
Swords Dance
I know it's a strange build. It has full speed, but it's not a sweeper. It has some bulkyness from EVs, but it has Swords Dance and Adamant. I'm not an idiot, it was simply an experiment.. at the beginning many throwed him at me as a good bulky sweeper, and many more used him as a very good physical wall, so I thougth: let's try to make him do both things. And I think it works... He's bulky enough to stall Excadrills and fighting types, and he can manage to take some Dynamic Punches. But in the second half of a battle... well... give him a chance to setup and he can easily sweep what remains of the opponent ;)

Volcarona (F) @ Lum Berry
Trait: Flame Body
EVs: 4 Hp / 252 SAtk / 252 Spd
Timid Nature (-Atk, +Spd)
Fiery Dance
Bug Buzz
Quiver Dance
Morning Sun
Trait: Flame Body
EVs: 4 Hp / 252 SAtk / 252 Spd
Timid Nature (-Atk, +Spd)
Fiery Dance
Bug Buzz
Quiver Dance
Morning Sun
My first sweeper and another standard set. Enter against a weak pokemon and Quiver Dance. Many pokemon are already doomed. And Supereffective Special Sweepers are one of the biggest mistakes opponents do. With one Quiver Dance he outspeed almost everything, even some Deoxys-S if I remember well. Couple it with another Quiver Dance and he have already doubled his Special Defense (which has a very good 105 base). You can throw any special attack you won't, no chance you will OHKO him, not even with a crit. And from there, the opponent is in a loooooot of trouble.

Conkeldurr (M) @ Life Orb
Trait: Guts
EVs: 252 Hp / 252 Atk / 4 Spd
Adamant Nature (+Atk, -SAtk)
Mach Punch
Drain Punch
Stone Edge
Bulk Up
Trait: Guts
EVs: 252 Hp / 252 Atk / 4 Spd
Adamant Nature (+Atk, -SAtk)
Mach Punch
Drain Punch
Stone Edge
Bulk Up
Another classic sweeper with another standard set. Being bulky and having Mach Punch he can ignore speed evs, but having 1 additional point often gives me the edge against other Conkeldurr... being able to Drain Punch before the other Conkeldurr can be the difference between a W and a L sometimes. Just find a chance to set up and then kill everything everything that breaths.
Team Strategy:
Simple. Start with Thundurus and mess up with opponent's lead. Volt switch and put a counter in the field. Then use Tentacruel, Ferrothorn and Gliscor to cripple, annoy and weaken anything that the other guy throws at me until I can predict something good or he makes a mistakes and gives me a chance to set up Quiver Dance or Bulk Up. When one of my sweepers is ready to go then everything is a lot easier. Stop.
In the past I often used complex strategies with baton passers, annoyers and more recently with a sand team. But I found that no matter how new or how cool your strategy is, it will always soon come a time when dozens of way to cripple you start to pop out from everywhere. And there you must build anything from scratch. This time I'm trying to use something that relies on my skill (which must constantly improve, obviously) more than in some strange tactic.
Thanks everyone in advance for your counsel :)