Sean
I think the idea that Jack and Locke would have been friends had the plane never crashed is amazing.
When the Nemesis guy talks about John's last thoughts...oh man. The stuff he says about Locke puts his whole character arc in perspective. Although we see it throughout, it's easy to forget since John always acts as though he has this extreme important, most of the time he didn't really know what he was doing, and he just wanted meaning in his life so badly.