In this country I think we could put Holden Caulfield on the list. Or we could until recently. Perhaps his influence has diminished, but for decades reading "Catcher in the Rye" and thinking you were the only person in your whole stupid world who "got" what he was about was a rite of passage. I'd like to say Huckleberry Finn, but I wonder: Is he influential -- in that he affects individuals' actions and thoughts -- or simply "important"?
I think this one has been going the rounds for a while! I think I posted mine on Petrona a while back but I am too lazy to go and look up the link now. I think my suggestions were pretty good, though ;-)