Runaway Train

Although Runaway Train has a ton of messages throughout the film, one of the greatest one's I noticed was that we live in an "every man for himself" world.  This is obviously one of the key existential beliefs, that we are all alone throughout life and we will die alone.  That idea is exemplified the most in the scene where Buck is trying to climb onto the top of the train.  We see this wide shot of him, a small man, on this huge, fast train(that could symbolize life?) and he's holding on for all he's worth, yet he keeps slipping.  As much as he keeps loosing his grip on the train, nobody else is there to help him but himself.  The isolation here is portrayed so well, since he is out in the cold, and then on top of that Manny won't let him in without a fight when he wants to give up and go back inside.  

Another place where this existential idea of isolation is shown is in Manny's line that was something like: "One must count on one's self, nobody else...There's no miracles in life!" 

That line is possibly one of the most important to the film because it sums up not only the point that we are all lonely, self-dependent creatures, but other existential ideas also.  It has the idea of no higher power or meaning to life, and the acceptance of a somewhat hopeless reality.