Go ahead and steal my idea.  Buy a hummer h1 and put very bright light bar on it.  Purposely grind your car against walls or whatever to give your paint scratches, dents, and sheit.  Install a train horn.  Now go drive it.  When you get behind someone being a douche hit the horn and flash your lights.  Maybe they will get the hint that you will run them over if they don't move.