Whenever we work on defensive tactics training at the dojo, we always do a form of rear naked choke. It has been called "The Great Equalizer", because it allows a small person to effectively defend themselves against a larger one. This makes it a perfect tool for people like myself. It can be effective either standing or from the ground, and it doesn't require the use of clothing. The guillotine choke, aka my second favorite sub, is also applicable for those reasons, since it is essentially the same choke put on from the front.
During my karate black belt test I was asked what my favorite technique was, and I said choking. In a self-defense situation, I don't want to be exchanging punches, trying to break arms, or resorting to eye gouging. If I can choke someone, then get the hell out of Dodge, that's what I'm going to do. Shihan always says "Let it make sense", and that just makes the most sense to me.However be warned: if you attack me and I am unable to choke you unconscious, I will gouge out your eyes and not think twice about it. Don't try me! Wouldn't you rather just take a little nap?