Someone mentioned krav maga earlier, that's a brutally efficient style which concerns itself only with taking the enemy out as quickly and efficiently as possible.
In a similar vein, muay thai or thai kickboxing (two names for the same style) is also brutal and efficient with flair only showing up in the advanced portions of the style. The basics are all about hitting hard and fast with your hands, shins, knees, and elbows; while preventing your opponent from doing the same. (yes, conditioning the shins hurts like the devil for a fair while, at first; but once you get used to it, it's like having a baseball bat attached to your knee.)
It's a bit tough to find a teacher, but most styles of ninjutsu are also built around the idea of quickly and efficiently taking enemies out of a fight. It's also generally coupled with teachings about how to read opponents and avoid notice, moreso than most styles; though all responsible teachers, in any style, will teach you the importance of avoiding a physical conflict if at all possible and a few basic means of trying to diffuse a situation before it escalates to combat.
Even western boxing can really shine in a street fight if you supplement it with at least some counter-grappling techniques from a style like jiu-jitsu or judo.
Btw, here's a dirty little secret that most traditionalist martial artists don't like to admit: there's no such thing as a single style that's good for all situations. Becoming a complete, well-rounded fighter requires at least some cross-training.
Oh, and someone said something about pain. Yes, training in the martial arts as they pertain to actual combat hurts. As long as proper safety is observed it rarely leads to injury, but it almost always hurts a bit if there's free-sparring, and it's exceedingly difficult to learn to read people's moves and to learn your reach and proper timing without at least some free-sparring.