Heracross for Pokemon X and Pinsir for Pokemon Y will be made available to North America players through a special distribution event from Nintendo.
Starting August 13 and ending September 17, Bug-type Pokemon Pinsir from Pokemon X will be made available for Pokemon Y through your 3DS wireless connection.
In turn, Fighting-type Heracross who is exclusive to Pokemon Y will be made available for Pokemon X through the same distribution method.
Also on August 18, owners of either Pokemon game can head over to their local GameStop and pick up a code for a Mega Stone that Pinsir or Heracross can hold. The code unlocks a Heracronite Mega Stone for Pokemon X and a Pinsirite Mega Stone for Pokemon Y.
When Pinsir holds Pinsirite, it can Mega Evolve into Mega Pinsir during battle, while Heracross will Mega Evolve into Mega Heracross in battle while holding Heracronite.
Finally, if you do head to GameStop for the Mega Stone code, pre-order Pokemon Omega Ruby and Pokemon Alpha Sapphire to get a special pre-order bonus poster.
Hope this helps!