Break something. When I get angry, I found that punching a wall only hurts me, and I know someone who bust up their fingers to the point they can hardly move one by doing just that. I also found punching soft things only feels pointless. If I punch something that's just hard enough to hurt me, but breaks or gives way in some kind, it helps.
Find something old, weak, and preferably wooden or plastic. Beat the ever-loving crap out of it. Best time I had venting my anger was when we needed to break down a rotting shed. I went all 'HULK SMASH' on it, and felt pretty happy afterwards; I had been productive and childish all at the same time. Is there anything greater than being rewarded for something childish and fun?