P90X - Chest and back.
I saw an article on Active.com about proper angry motorist etiquette.
"I understand the impulse when a driver has just pulled out in front of you or turned directly in your path or otherwise behaved like a jerk. I know how much you'd love to slap the trunk of that driver's car, or shout at the person behind the wheel, helpfully suggesting that he or she "learn to drive." Or extend a certain digit in a certain direction. Do yourself — and all runners — a favor and fight that impulse. Smile. Your lashing out isn't likely to change the driver's behavior, and may, in fact, worsen it. For all you know, the still-seething guy may drive extra close to the next runner he sees, just to make a point. Let him go."