One of my favorites is...bringing the back foot up to the front foot, as I am throwing out a head punch, with my lead hand, then, quickly, push my front foot, foward, and connecting to the chest/stomach, with a reverse punch. This is a all or nothing attack..as once you start, you move fast and you don't stop, so if a punch comes at you, you must deflect as you are constantly moving forward. This combo, if done right, can really make up distance on your opponent, which is what makes it all the more effective.