The only mons that are banned atm are : Mewtwo, Ho-oh, Lugia, Kyogre, Groudon, Rayquaza, Palkia, Dialgia, Giratina, Giratina-O, Arceus, Zekrom, Reshiram, Darkrai, Shaymin-S, Xerneas, Yveltal, Kyurem-W, Deoxys-A, Deoxys-S, Soul Dew.
Deoxys-D, tornadus-t, genesect, are not banned atm, you are free to use them as of now. The next tiering period will take place early in 2014, so they may or may not be banned depending on the dynamic of the metagame. (I dont know about others, but I think genesect should never be allow to walk in the face of OU again, this thing is jack of many trades and master of all).
I finally got a chance to play X and Y yesterday on PO, theres this mon I used called Talonflame which can potentially be a huge threat. It can learn brave bird and gets gale wings ability which makes all flying attack priority, so priority brave bird bitchesss. Also it can learn bulk up and flare blitz.
Greninja ability protean is actually pretty cool and its a very fast mon with spikes and tspikes, too bad its not a genesect and cannot boost any of its stats.
I think you can use drizzle+swift swim as I've seen some ppl used it, im not sure if they forgot about that or just allowed it to be played in OU.