I never really noticed that Viggo had various accents, I'll have to pay attention next time.
Sam always sounded like he spoke with an American accent and rural British frases: "there's nothin' for it" and "if you understand me", to name a few. I'm not sure if he spoke in a British accent ever.
Elijah did a pretty convincing job, exept in one spot: where he and Sam camped outsidd after seeing the Elves. After Sam complained about a root sticking in his back, Frodo tells him to think of his bed at home. Elijah's line right there sounded SO American, it distracts me.
~M