What is the most effective and most practical fighting style? ?

I would like to learn a practical fighting style that is not just popular and or for show, not that that's all fighting style like karate are, but I get the feeling that I should start something else. I'm not really talking about an all defensive style either I want to be able to drop someone in a fight fast. I was thinking something that special operation divisions are taught. I hear Moi Tai is a good style but I don't know what it consists or if I spelled it right.