Yes, I mean the trope. Who is your favorite protagonist who does not take the center stage... okay it'd be easier to use this.
http://tvtropes.org/pmwiki/pmwiki.ph...ingProtagonist
Anyway, here's a couple of mine.
Lucy (Fairy Tail): A down to earth character who allows the audience to ease into the story, since she's just as flustered as us. I originally didn't quite care about her, focusing more on Natsu who was The Hero, but she's really evolved I think. Going from something of a curious fangirl, to a courageous person who'll protect her friends.
Zenkichi(Medaka Box): I initially thought that Zenkichi was a tired archetype; the ordinary high school student who is always surrounded by more interesting people. But by the end of the first chapter, he drew me in. Just as determined as anyone else in the story, he brings out a positive aspect of human nature.