edit: Got all the mega stones... all I really need now is a legit Arceus.
I recently finished Pokemon X for the second time and now I have some extras I wish to trade for the Pokemon Y exclusives. So that mean I want to trade a...
Xerneas for Yveltal--Already Traded
Mewtwonite X for Mewtwonite Y--Already Traded
Charizardite X for Charizardite Y--Already Traded
Pinsirite for Heracronite--Already traded
Manectite for Houndoominite--Already traded
Tyranitarite for Aggronite--Already traded
I do have extras of the other megastones in case for some reason you wanted to trade a Y exclusive stone for an extra non-exclusive stone, but since I imagine only people that completed Pokemon Y twice or plan to will be interested, they'll be after the exclusives only.