A GALACTIC TEAM
I would like to build a team around CM Jirachi. It is a good poke with nice stats, a spectacular moveset, and also because of Serene Grace; a feared and annoying trait.
I played with this team just few times, because I tried to do it in paper first. Please I need improvement here, there is some little things to be covered as soon as possible...
Supernova: in state of boom...
Metagross @Occa Berry
Adamant Nature
252 HP / 236 Atk / 12 Def / 8 Spe
Metagross was chosen as my lead for some specific reasons: almost a safe stealth rock setup, priority, safety against some common leads, and explosion, being a compulsory move in any team, wrecking against my opponent. Most of the time, I try to keep it alive and just explode when the time comes. Occa Berry is used to face lead Apes and Heatrans, and also Fire Blast Azelf. THe ev's spead are standard though.
Neptune: lord of the ancestral seas.
Swampert @Leftovers
Impish Nature
240 HP / 52 Atk / 216 Def
Sleep...Burns...etc..are always annoying for everyone. Apart from being a nice wall, Swampert is my status absorber, resting and sleeping around. Avalanch was chosen due to Dragon Dance Salamence. It keeps Tyranitar away and Gyarados sometimes. I'm considering Stone Edge instead of Avalanche to blow Gyarados away though.
The Meteor: crossing the universe
Latias @Choice Scarf
Timid Nature
252 SpA / 4 Def / 252 Spe
The Revenge Killer, and main Ape counter. Draco Meteor opens big holes to my opponent's team, really useful in some circunstances. It atracts scizors and blissey, so there are special gifts for them: hidden power fire and trick. Thunderbolt is mainly for waters. Timid was chosen becuase the extra speed is needed to revenge nasty, speedy things.
The Alien Beast: made to destroy
Tyranitar @Choice Band
Adamant Nature
176 HP / 252 Atk / 80 Spe
Made to be a murderer, tyranitar's main and unique role is to kill. Nothing else. Pursuit rapes Blisseys and Gengar, coming into Latias mainly. Fire Punch is my answer against scizor. This set requires lots of prediction, but it works. Rotoms forms are annoying though, I hate to fall into a will-o-wisp, so I always check it with swampert, but it is sometimes a risky desition..mindgame is not my best skill, luck is preferred in the mayority of the cases.
Metagross @Occa Berry
Adamant Nature
252 HP / 236 Atk / 12 Def / 8 Spe
Metagross was chosen as my lead for some specific reasons: almost a safe stealth rock setup, priority, safety against some common leads, and explosion, being a compulsory move in any team, wrecking against my opponent. Most of the time, I try to keep it alive and just explode when the time comes. Occa Berry is used to face lead Apes and Heatrans, and also Fire Blast Azelf. THe ev's spead are standard though.
Neptune: lord of the ancestral seas.

Swampert @Leftovers
Impish Nature
240 HP / 52 Atk / 216 Def
Sleep...Burns...etc..are always annoying for everyone. Apart from being a nice wall, Swampert is my status absorber, resting and sleeping around. Avalanch was chosen due to Dragon Dance Salamence. It keeps Tyranitar away and Gyarados sometimes. I'm considering Stone Edge instead of Avalanche to blow Gyarados away though.
The Meteor: crossing the universe

Latias @Choice Scarf
Timid Nature
252 SpA / 4 Def / 252 Spe
The Revenge Killer, and main Ape counter. Draco Meteor opens big holes to my opponent's team, really useful in some circunstances. It atracts scizors and blissey, so there are special gifts for them: hidden power fire and trick. Thunderbolt is mainly for waters. Timid was chosen becuase the extra speed is needed to revenge nasty, speedy things.
The Alien Beast: made to destroy

Tyranitar @Choice Band
Adamant Nature
176 HP / 252 Atk / 80 Spe
Rider of the Astral Planet
Lucario @Life Orb
Adamant Nature
252 Atk / 4 Def / 252 Spe
My Physical sweeper, taking approach from Sand Stream and Stealth Rocks, after a single Sword Dance, lucario is an effective sweeper. Close Combat nails Stall, and extremespeed is imo the best priority move in the whole game. Substitute is a little bit trick, but it saves me from status, and allows a free SD before the sub breaks. I'm open minded to accept any suggestion concerning the last slot.
Lucario @Life Orb
Adamant Nature
252 Atk / 4 Def / 252 Spe
The White Star: It's time to shine!
Jirachi@ Leftovers
Timid Nature
252 HP / 176 Spe / 80 SpA
The thing that inspired me to build this team. Calm Mind Jirachi is awesome, able to kill blissey 1vs1 in the mayority of the cases. After some calm minds, there are few things that can resist a rampage like this. Charge beam works in conjuction with Serene Grace, increasing my SpA to high levels in just some turns. Flash Cannon has been considered instead of Psychic, but Psychic is better to beat Lucario after some Close Combats. 
Jirachi@ Leftovers
Timid Nature
252 HP / 176 Spe / 80 SpA
So that's all folks. Please rate my team. All suggestions and criticism are appreciated!