Elizabeth/Jack, post-World's End, "I must go down to the seas again, for the call of the running tide / Is a wild call and a clear call that may not be denied" (full poem here).
Sean/Viggo, Sean comes to visit Viggo during long stretch of time while they're filming Helm's Deep, "How do I know what I think, until I see what I say?" (Attributed to W. H. Auden, quoting a child.)