I agree with Soul Fighter on... Most all martial arts improve your skill...
Basic Kickboxing though takes skill to master... It teaches the basics of kicking and punching effectively... Hitting Hard Fast.. Plus it is one hell of a cardio work out that will get you into top shape.. (Krav Maga, Karate, Wushu, Kenpo, TaiChi, Muy Thai, Aikido, Yadda Yadda Yadda are all good)
Do your research.. make sure its a good school and not a "black belt factory".. a BBF will more often then not give you a black belt and only have taught you half the stuff a "real" black belt would have earned..
All in all.. Like most skills in life.. MA takes conditioning.. Practice.. Practice.. Practice Untill the moves you are performing is what you will now Naturally do in a fight.. if you condition yourself to block or strike a certain way in a fight... that is what your body will do.. because in a fight.. you do not have time to think... being that I hope you are not a bully and using this to hurt others...
You will be forced to be in a Reactive mode(defense).. which means.. responding to an incoming threat which has started before you began defending... Through conditioning and very important.. sparring at full speed (wear gloves guys haha).. Your body learns what works.. and what doesnt... do you know how it learns what doesnt? YOU GET HIT!
haha.. best to learn these lessons in a Dojo(classroom) Instead of while being attacked by Thug 1 and Thug 2..
Judo is also an effective real life situation combat MA.. alot of the movements are able to be used on the street and is the art that is taught to the police in Japan..
BJJ is great for in the ring.. and if u end up on the ground in a fight.. sure.. but try getting an armbar on someone while his buddy is stomping on your head.. No Bueno..
*NOTE* Street fights are sloppy... most street fights are fought uncoordinated and wild... Your opponent though may be skilled.. while under stress often will not hit you with a *proper strike* If you have not conditioned yourself to improvise in situa
Weapons Fighting... I would Def recommend which has a few names for the same damn thing... Arnis, Kali, Eskrima.. Often taught with Kali/Eskrima sticks.. but the same motions are used for knife fighting..
*NOTE* You never want to EVER be in a knife on knife fight with someone.. In most cases even if you are skilled.. You will be cut.. Knife slices and puncture wounds are NASTY and very Dangerous.. do to all the sensitive blood vessels in the body along with everything else...
Though.. if in a knife fight or having to use a knife in a self defense mode.. Best to be skilled with one.. then unskilled..
[youtube]
http://www.youtube.com/watch?v=LVnx0NHnekQ[/youtube] Great example of this...