Self defense and avoidance are great discussion material. Some very useful posts, and I must also add my $.02.
A little about my background, started martial arts in 1984. Have studied Taijutsu, Aikido, Bushido and Gracie Jujitsu before mastering Army
Combatives, which it is based on. I've been taught that, if a fight lasts 3 seconds, it is taking too long.
The replier who mentioned multiple opponents, more probable than any other situation. When someone gets into a physical confrontation, some one is
outnumbered. I've been there, know it first hand, and won.
From personal experience, I swear on Aikido being the best martial art for defense. It teaches one to deal with multiple attackers, ten being what I
was able to handle with confidence. The fact that Aikido is purely defensive with out one attack is amazing.
Being able to use it, with other forms with attacks is devastating. I highly suggest every one interested in greatly increasing their confidence and
skills in physical confrontations to study Aikido as a martial art.
Just imagine Steven Seagal and Hoyce Gracie combining fighting techniques. That's what you get with that combination.
Just hope that gives an idea of options available. It's better to have a specalised tool in your tool box and not need it. Than it is to need it, and
not have it.
Avoidance is the best course of action, and often the easiest way to bypass an obstacle is to go around it. Just be ready when the obstacle refuses to
get out of the way.