My all time bread and butter stike is a left hook off a jab combo. Flick the jab part way out then shuffle into a left hook. It works a lot like a sucker punch and beacuse I like the left hook so much,,and have practiced it ad- nauseum,,,it's also my hardest hitting punch. It's targeted to the jaw, nose or temple. Ive scored several street knockouts with it and gained the initiative in a number of other fights by throwing it. There's no predicting how a fight will shape up but I nearly always start the festivities with my all time fave. K-

Just my two cents worth: After giving it some thought, I finally came to the conclusion that what you naturally do in a non- fight scenario is the appropriate thing to do in a fight. E.g.: If you're coming in the door with your arms full of grocery bags, don't you naturally close the door with your foot? Unless a wind gust suddenly starts to slam the door, threatening to smash your toes, in which case you might switch perhaps to using a shoulder on the door.
Likewise, I'll use my hands in a fight unless it's impractical (I've been grabbed by the arms, or the opponent retreats out of arms length) and I can successfully kick or use a knee. It's an old concept in the MAs that when you use a hand strike you're standing on both feet, but when you strike with your legs, it's only the one, with the concommitant loss of stability.