Truthfully if you are interested in defending yourself stick to a jab and a straight right to the body. I have ended many would be confrontations with those 2 punches. The jab if executed semi-correctly is more than enough to break a nose, tear up the eyes, interfere with breathing and it keeps you in a good defensive position and at a distance from any surprise blows. The straight right to the solar plexus (generally wide open after the jab to the face) quickly ends most confrontations and if for some reason it does go on from there I guarantee their desire is fading fast. The body punch targets an unexpected area, interferes with their breathing and takes all of their punching power away.
A haymaker is easily avoided or countered-if by some miracle it lands your hand will most likely be broke and if they dont go out you are left defending yourself with 1 hand.
Lastly a side step or drop step will save your face better than any haymaker and will put you in a position to do serious damage with your jab