Haii people. 
Anyway so, here I am with Valet, also known as Jojo, also known as Aeternis etc. my Databse brother (Sempi and Aeternis :3) with our first joint RMT together, as well as one of the first (Maybe the first? I don't know >.>) Gen 6 Pokebank Uber RMTs so far. 
Josh and Jojo. Alliteration. Yush. And yes my name is Josh like the many other couple hundred users on this site called Josh. Booo.
Anyway so yeah, with both of us having played Ubers a bit, we decided to make a team together to enter the new generation, which brought in new threats in the form of mega-pokemon and the new type, Fairy which made Dragon Types run home with their tails between their legs. 
How to cause the Apocalypse
So the moment we got onto our pad and decided to build a team together we had to include one of the newly introduced ubers - so we had a pick between Xerneas and Yveltal. After much deliberation, we decided Xerneas was basically too mainstream and threw it out the window, to give Yveltal some glory on our new team. In regards to what Yveltal would do, we had a look at it, and decided that with it's nice speed and excellent offensive stats, to make it a scarfer. So yeah, wow we had our Revenge Killer all done right off the bat. XD
So after that, we decided to grab something that would at least somewhat cover Yveltal. To make this a little bit quicker, here's what was up on our pad right after Yveltal made his star debut on our team;
>Let's see.......weak to electric...which is quite common....weak to SR....so we will most likely need a spinner/defogger....weak to Rock...which is uncommon....weak to Ice....which is still uncommon besides Kyogre's Ice Beam....and the rare Arceus-Ice......weak to well I think that's all T^T
Perhaps a Pokemonmon that enjoys electric type attacks and that can mind a paralysis
Oh and maybe...just maybe a spinner/defogger....
You get the gist. Anyway, so we debated utilising Arceus Ground because it could take Electric attacks with ease (Because it's immune), as well as Rock attacks. We also decided to use Defog as our choice of Hazard-Remover over Rapid Spin, so Arceus-Ground could function in that role too.  However, after staring at our pad aimlessly, we decided that the dual Ice Weakness Arceus-Ground provided wouldn't be nice and decided to go an extremely wierd direction - Support Arceus Electric. It gave us a pokemon to take Electric attacks, wasn't weak to Ice, and was also a solid check to Ho-oh and could take on some variants of Kyogre. 
Our next pokemon we decided on was Florges, one of the new Fairy type pokemon. Why you ask? Florge's massive special defense and decent enough HP allowed it to be our lovely Dragon Counter- and more importantly stopping people with a Flower has got to be one of the best things ever. And it's b00tiful! Additionally Florges was an excellent response to alot of the major uber pokemon (I'm looking at you Palkia), and also provided us with Wish Support. Blissey saks k?
So just a quick recap. Yveltal, Arceus-Electric and Florges on our team so far.
At this point we realised will still needed to address the pressing problem of Xerneas, who right now rampaged unchecked through our team. And then we saw it. Guess plz? :3
Mega Scizor of course.
So Mega Scizor's fantastic attack and defense, as well as good special defense made it an instant standout, and it's ability to kill Xerneas with a Technician Bullet Punch, as well as set up a Swords Dance with ease made it an instant bringer of doom and death. So of course we'd stick it onto this team.
Alright. So next up we decided that we wanted a Tank. 

Oh wait wrong one. Eerrm. Well in truth we never actually ended up with a tank of any kind. We ended up using a wall. A Great Wall. A Giratina :D
An excellent counter to Extremekiller Arceus, as well as other boosting pokemon who Giratina can just phaze out and physically based pokemon who Giratina can just burn. Also providing a good counter to Mewtwos utilising a Psystrike + Aura Sphere combo, and the Mega Forms with burn to screw up X and Y is basically the normal one but stronger. ^_^
So here comes the hard part. The last pokemon. This one took us the longest amount of time, as we were really unsure what pokemon to use. We considered one of the staples from Gen 5 and before, Kyogre, but the weather nerf put us off, and the fact Kyogre didn't do anything particularly important for our team. However, another look at our team showed us we lacked a little in the Physical Department - so we settled with one of the old ubers who got thrown into OU, but was still a great pokemon for Ubers (And I have no idea what I'm saying) - Blaziken. So this chicken, in all it's blazing glory became the last member of our team, with it's high attack and awesome speed boost ability. We decided that we would replace it if it failed epically - but luckily it didn't.
Synergy
It really sucks that Marrilands doesn't support Gen 6 properly yet. T^T
Type                            Resist                           Weakness
Normal                      Scizor, Giratina
Fire                        Giratina, Blaziken                   Scizor
Fighting                    Giratina, Florges
Water                       Giratina      Blaziken
Flying                      Arceus        Blaziken
Grass                  Blaziken, Scizor, Giratina, Yveltal
Poison                      Giratina, Scizor                     Florges
Electric                    Giratina, Arceus                     Yveltal
Ground                      Yveltal                            Arcues, Blaziken
Psychic                     Yveltal, Scizor                      Blaziken
Rock                       We-has-will-o-wisp                    Yveltal
Ice                         Blaziken, Scizor                 Yveltal, Giratina
Bug                   Blaziken, Scizor, Giratina, Florges
Dragon                      Scizor, Florges                      Giratina
Ghost                       Yveltal                              Giratina
Dark                  Yveltal, Florges, Blaziken                 Giratina
Steel                       Blaziken, Arceus                     Florges
Fairy                       Scizor                               Blaziken
Replays and Rating
Showdown replays not working, ladder saks. Later.
VS CS Gen 6 Team
Vs Pika Master
Vs Guy who was 2062 rating on the ladder
Replay 4
Replay 5
Replay 6
Some more on the pad, I'll fetch them later too.
Aeternis - 1776 
Sempiternus - 1583
 (Yes we've both barely laddered. I've done like 6 matches, Aeternis has done like 15 :P)
Anyway team in detail coming in the Answers with Jojo.