VOY: Janeway, Tuvok, Belanna
Or, from season 4 onwards - Janeway, 7 of 9, and the EMH.
Though I'd argue that TNG and DS9 did it less then TOS, VOY or ENT.
Though in the latter two cases, it seems to be less a starting idea and more of a 'this is who people want to see so we'll put them on more' (or, for the cynics - 'this is who some/stupid people want to see so we'll put them until we do them to death )
later days!
Mark
'Wish I could Help you....Wish I could tell you,
That I am real, I'm not something you invented,
That I'm not everything you want me to be.'
'And I am...Ageless. And I am....Invincible.'