Quoted By:
Fire/Fairy
Water/Dragon
Grass/Steel
Gen 6 had the Fighting/Psychic/Dark core with its starters. Now we have the Fairy/Steel/Dragon core of the current competitive metagame.
Water/Ice
Fire/Rock
Grass/Bug
The starter typings paired with a bad secondary typing, in order to help encourage the player to use their starter as a starter Pokemon in the truest sense of the term: A Pokemon they can rely on as a crutch during the early game but one they'll want to replace later on.