From a technical standpoint, this piece is simplistic, but to the point. The cross hatching in the shirts of the two characters is well done, and adds a sense of tactility to the illustration. The faces are for the most part iconic, but it works for this piece. The two-toned color scheme works well, since it is suggesting a battle between the two characters. I really like how their faces are represented by "facebook" and "myspace". It's difficult to find a way to visually render abstract concepts like social networking sites, and I thought this was a very clever and creative way to go about doing it.
Though I appreciate the representation of the characters, I feel as though the idea of pitting them against each other at gun point is not the most original way to represent them in battle with one another. Perhaps this is just my own personal taste getting in the way, but I feel as though it has already been done before, and that even a concept as old as a one-on-one face-off still has creative potential that is yet untapped.
But alas! in typing this critique, I just realized something more clever that you did in your piece. I just made the connection with the two men to the classic myspace person icon.
Overall, I think this is well-thought, simplistic, to the point, and a professional quality illustration.