Major spoilers: seriously, watch the film before reading this or it'll ruin an amazing experience.
Usually trailers are pretty good predictors of what films will be like, but in the case of Looper (2012) the trailer does not do it justice. Touted as a time travel action yarn, it ends up being a great film that radically departed from Hollywood's cliches.
The film takes place in 2044 (the "present") and 2074 (the "future"). In a depression plagued future, time travel is discovered and immediately outlawed. However, since society is run by powerful crime syndicates, time travel is utilized illegally.
In this comes the film's brilliant answer to problems with time travel: no one knows how it works. Since time travel is run by self-interested gangs, its workings are unknown and ambiguous; if paradoxes emerge they are simply assumed to be correct. As Roger Ebert says, Looper "sidesteps the paradoxes of time travel by embracing them."
In this dystopian future, time travel works like this: when gangs need someone killed (because disposing bodies is impossible due to tracking technology) they send the person back in time where a hitman (or "looper") immediately executes them and disposes of the body. Eventually, even the future selves of loopers are sent back to be killed (to avoid links with the gangs, thus "closing the loop") and a large retirement package is awarded to them to get out of the business for good. If they let their future selves go, the consequences are gruesome.
Here enters Joe, a looper played by Joseph Gordon-Levitt who eventually has to kill his future self, played by Bruce Willis. Something goes wrong. His future self fights back and runs away.
We then see the life future Joe has made for himself. Traveling to Shanghai he gets married and discards a life of drugs and crime. However all that changes when a new crime boss, known only as "The Rainmaker" kills his wife and has him killed (or should I say "looped") by his former self. He avoids this fate and is out to kill The Rainmaker as a child.
Here we have the first big break with Hollywood cliches, we know (or at least assume) that time travel is a one way street, you can only go back in time. So him killing The Rainmaker as a child won't necessarily bring him back into the future, or put another way, he will be marooned in the past no matter what.
As the two Joes meet in a diner, the young Joe gives the obvious solution: future Joe should tell him who his wife will be so he will never marry her and thus never put her life in danger. The outcome will be the same, his wife will be saved but with the caveat that he will never meet or know who she is. Future Joe rejects this and ends up hunting for the Rainmaker anyway, going to the point of murdering children.
Thus we realize that he's not actually after the safety of his wife, who he can much more easily save the other way, but to preserve his memory of his wife. This narcissism becomes even more apparent when, after murdering a child, he cries about not being able to see his wife, not the heinous crime he has just committed.
This seems like a clear rebuttal to Hollywood's amoral familism. Instead of apparently "heroic" fathers doing whatever it takes to save their families, Joe is murdering children in order to preserve the vanity his wife provided him. Even more so, Bruce Willis, the iconic action hero, becomes the villain in this regard.
In the meantime, past Joe finds a farm which has a possible young Rainmaker, in this case a 10 year old with a single mom. We discover the child is highly intelligent but has serious emotional issues, the most likely prime candidate of the Rainmaker. Despite his earlier skepticism he ends up defending them from his future self.
Here we have the dramatic irony of the film, while the future Joe has decades more experience, the experience leads him to be even more narcissistic while the recent events make the younger Joe more selfless. This reaches its dramatic conclusion when (seriously if you read this far and haven't watched it you have a final opportunity here) the younger Joe scarifies himself to stop the future Joe and save the wife and kid.
This ends up being radical for two reasons, on the one hand a man killed himself to save a single-mother and a child (people that are typically stigmatized) and secondly, he assumed that the change he made will redeem the child from being a crime boss in the future. Probably the most "pro-nurture" move in a film in decades both in terms of moms and the nature vs. nurture argument.
While most reviews focus on the time travel logic or quality of the film (which this does to an extent as well) its worth noting that politically its a rather good film as well.