Since I was one of the folks who said I would not opt for fisti-cuffs, I'll put another response in here.
First of all, avoidance in the best defense in such situations, and I guess sometimes, it can not be avoided due to poor planning, and a lack of situational awareness (a skill that I would argue is more important than h2h combat, and something that actually can be learned, and requires training for upkeep), or just crappy luck on a certain day. So, lets say through whatever reason, I find myself backed into a corner, with no viable means of escape except through physical violence. I have tried to de-escalate verbally, and that did not work. I have tried to peacefully leave, and that did not work.
My EDC gear consists of my carry gun, two spare mags, Spyderco Endura, cell phone, wallet, and keys. I don't really want to wear a Batman belt as a civilian. As an infantryman, I have pretty extensive training in my service's martial art, which is not taught at Mc-dojo's, and places an emphasis on real fighting. I have trained and practiced both non-lethal techniques, and lethal techniques (more training on this, obviously we can't kill our sparring partners).
My first choice at this point would actually be my cell phone, especially in a scenario such as AZ Infidel's where there is a barrier. Call 911, start explaining the situation, and let them record what is going on, and hopefully get some help on the way.
If the phone doesn't work, or someone puts their hands on me, I am going to respond in whatever way I feel necessary in order to defend myself, while using appropriate force according to the continuum of force. I have attempted to de-escalate and escape, and through no fault of my own, it did not work. There is a viable threat to my well being. What if the guy gets me in an arm-bar, that can certainly cause grievous bodily harm, or he kicks out my knee, handicapping me for life? Do I need to wait for him to do that before I can defend myself? Even if I go hands on with him, there is a chance that a jury will see me as using too much force if I dislocate a joint, or break a bone. Because I am a trained killer with combat experience, and will be for the rest of my days. So why did I need to go that far on a drunk who wouldn't let me leave?
Someone said taking a life is the most serious thing you can do, if you read my posts here, I have said that in other threads. I am very aware of how true that statement is. If for the rest of my days I don't shoot another human being, I will be happy. But I will not allow someone to cause me serious bodily harm or kill me if I can stop it from happening. Of course, there are a million variables to this, including each individual who carries and their training/skills/size/general health, and the BG's apperance/size/intent/words/posture (and the same if he has any friends). But that is my answer for me. Everyone else needs to come up with their own answer.
Of course, in every fist fight I have ever been in, there was always a point where I could of walked away from it, and for stupid or not so stupid reasons I didn't.