As they can become any type (except typeless and Shadow), they get STAB on every move. If you mean legitimately, for Pokemon that get the Ability:
Protean (Keckleon and the Froakie line) do not learn Fairy moves, so they can't get STAB on Fairy moves.
Libero (Cinderace line) do not learn any Grass, Water, Ice, Dragon, or Fairy moves, so they can't get STAB on moves of those types.
...the user will receive same-type attack bonus on every move it uses (except Struggle)
Hope I helped!