EDIT: The code for Samurott is POKEMON503.
Pokemon Omega Ruby and Alpha Sapphire are having a distribution of all three Unova starters. All three distributions will end on November 30th 2015, however, only Serperior and Emboar are available now. The three Unova starters have unique hidden abilities that are not normally obtainable. As of now, only two of these hidden abilities are confirmed to be Contrary,and Reckless. To unlock the Pokemon for this distribution, after pressing start on the title screen, you must go to “Mystery Gift” in your Pokemon Omega Ruby or Alpha Sapphire game, select “Receive Gift” and then select “Get With Code” and put in the code POKEMON497 for Serperior and POKEMON500 for Emboar.