Chigurh's Coin Toss
The fact that Chigurh offers the store clerk, and later, Carla Jean Moss, the opportunity to save their own lives by correctly calling heads or tails when he flips a coin, is a symbol of his complete disregard for the value of human life. To him, a life is only of value to him if he is being paid to take it. If he is not paid to kill someone, he has no real objection to leaving them alive, but he turns it into a game for his own amusement, another symbol of the fact that he views a human life as entirely disposable.
Coin Symbol
Chigurh urges the store clerk not to put the coin into his pocket. If he does this, it becomes just that - a coin, and will sit with the other pocket change that he has until such time as he wants to spend it. If he treats the coin as something other than than that though, then it becomes a symbol of life or death, because if he correctly calls heads or tails then he saves his own life.
Random Nature of Life Motif
The nature of everything that happens in this movie is completely random. It does not follow a pattern, or show a life that has a cause and effect, or even a series of consequences. This is exemplified by Chigurh's habit of deciding whether people should live or die at the toss of a coin but also extends to the way in which some characters meet a more brutal end than others based on nothing more than a series of random facts and occurrences;
Bad Ends for Good Characters Motif
This is rather an upside down scenario given that in most stories the good characters come out safe and sound at the end whilst the bad guys get their comeuppance. Not so in this Coen brothers movie where there seems to be no delineation mark between the results for those who are bad and those who are good. Chigurh, a psychopathic assassin, meets the brutal end he deserves; but this is not so dissimilar to the fate that awaits Moss's wife, Carrie Jean, who is in danger purely because her husband was killed by a hitman who now wants to kill her as well. There are no rewards for virtue in the film, and this is a constant motif that appears throughout.
Time to Retire Symbol
Bell realizes that he is several steps behind the men he is in pursuit of, not just physically but in terms of what they are capable of, and of what they are prepared to do in terms of the violence they are prepared to engage in. This inability of his to comprehend the increase in violence, and the fact that the criminals are always ahead of him, symbolizes that it is time for him to retire.
