I'm a big fan of the gut punch which transitions into a hair-pull down into a knee to the face combo.
If you don't wear pants, the blood is easier to clean off.
@Tfmonkey I like the fake telegraphed punch that is actually a kick to the groin while your fist pulls back. From there, the process is the same. Knee to the face while "helping" their head down. For flavor, add the thumbs into the eye sockets right after, which I hear you're a fan off too. *chef's kiss*
@RoninGrey Well, these type of combination techniques only seem to work in movies; against an attacker who is not resisting. More often than not, you will be taken by surprise and overcome. Especially if you telegraph you are an easy target. Best to go straight for the eyes to disable. Better yet, present arms and open fire.
Thing is: Now you are open to lawsuit for "mutual combat", unlawful draw, and unjustified use of force.
@sardonicsmile
The biggest reason these things fail, in my opinion, is related to what you said -- everyone thinks they're going to get first blood. You have to spend a huuuge amount of time getting used to receiving incoming hits, actually being hit, and being able to make something happen amidst it. And as you said, the BEST way to win is to avoid the fight altogether.
But I have used a light knee to the gut of a much larger opponent and made him react in a way that would receive a face-knee.