The comic book world is shocked by Marvel's recent decision to kill off one of the most iconic superheroes - The Hulk. In Civil War II #3, just released this past week, Bruce Banner was shot by a one of Hawkeye's special arrows, one that he made himself to give to Hawkeye. He told Hawkeye that if he was suspect of going on a rampage, then just kill him, which is what Hawkeye did.
But he'll probably be resurrected sooner rather than later in the Marvel Universe somewhere.