I have not read them all, but for me it would either be Moby Dick or Huckleberry Finn. I think Huckleberry Finn edges it. It is like nothing else I have read, and it really came alive. It is very funny. The best bit for me is when the clever girl keeps catching out Huckleberry Finn in his lies. Nevertheless, it nearly loses first place with its last few chapters. Moby Dick is very long and slow, but it picks up steam towards the end. I loved the discussions Ahab had with individual crew members; I seem to remember with a Manxman in particular.