The [url=http://www.serebii.net/itemdex/ovalcharm.shtmlxfl]Oval Charm[/urlxfl] has returned in Gen VI! I'm sure everyone could find it very helpful for breeding.
You receive it from Professor Sycamore after you've seen/obtained 150 Pokémon in each of your Kalos regional dexes (central, coastal and mountain). This excludes Mewtwo and the roaming birds. If you have crowns next to the regional dex on the beginning Pokedex screen, you've completed that region's dex. Go to Sycamore and have him evaluate each of the three and when you've shown him the last one has been completed he will give it to you.
It is a [ixfl]key item[/ixfl] so you can't be accumulating more than one per game.