You say you have tried everything. Does that include emphasizing the positive aspects of his personality? Empathizing with whatever it is he wants that he can't have? Making sure that whatever his usual triggers are get minimized to the greatest extent possible?
If you wonder how in the world one would emphasize the positives and empathize without making his behavior worse, check out the lovely and practical book How to Talk So Kids Will Listen, and Listen So Kids Will Talk, by Faber and Mazlish.
If you've already tried those techniques, and he hasn't improved, then medical evaluation might be worthwhile. And here's one more angle that could be fruitful:
A very large and well-controlled British study a couple of years ago confirmed that not only several common food colors, but also the preservative sodium benzoate made hyper kids measurably more hyper. See a report here: http://www.consumerhealthreviews.com/articles/GeneralHeal... Or he may have other sensitivities/allergies that make him physically or mentally uncomfortable and hard to please. He might be sending out signals for help but have no real idea why, if he's just always at odds with his own body.
I have severe chemical sensitivities, and get both physical and emotional symptoms to exposures to perfumed toiletries, home cleaning products, fabric softeners and air "fresheners." In group testing situations, I have watched children go from contentedly coloring to bouncing off walls, screaming, crying, or being impossibly stubborn just minutes after having drops of some dilute solution squirted under their tongues.
It would be worth checking out. You can try sealing all suspicious products in plastic bags and using baking soda or vinegar for most cleaning for the next 2-3 weeks, and watch for any improvements in your son. If reintroducing the products (many of which are toxic, anyway) back into the home then results in worse behavior, you'll have a possible solution to work on.