"he might come and ha'nt us..."See in text(Chapter X)
Jim means this in both a literal and a figurative sense: the dead man's ghost will come to haunt them and the image of the dead man's body in the house will "haunt" them psychologically, reminding them of the horrors of death and murder. It's important to note here that there is a "ghost" haunting Huck throughout the book: his father, whose abuse make him run away and whose whereabouts Huck won't learn until much, much later.
"they seemed to come up dim out of last week..."See in text(Chapter XV)
Here we see that the fog has become a metaphorical fog in Huck's mind, preventing him from understanding where he is, why he's here, and what happened to him. It's significant that Twain chose to create this fog almost exactly one-third of the way through the novel, when Huck feels so far away from his past life in the city that he begins to shed that personality. After this fog clears, he comes back to himself slowly, quietly, and with a sense of mild surprise. Is this his life? Yes.
"my! how that snag's tearing along..."See in text(Chapter XV)
This is a metaphor for Huck's journey: as he travels down the river, he doesn't stop to think about how fast he's going in comparison to the rest of the world and how much more he knows than everyone else in his life, particularly the ones he leaves behind. He thinks he's just the same old Huck, but he knows that Jim's innocent, that there was no murder, and that he himself isn't dead. These things will lead him to make some conclusions about race, society, and his place in it; but for now anyway he thinks he's just sitting still.
"you could see where pieces had got chipped off..."See in text(Chapter XVII)
These ornamental fruits are a metaphor for the Grangerford family, which, though well-to-do, has begun to lose its veneer of breeding and good-manners, have engaged, as we'll soon learn, in a long and foolish feud with the Shepherdsons, their enemies. Thus, though the Grangerfords may appear rich and comfortable, the reader knows that, underneath, they're no better than Huck or the Shepherdons.
