Are you talking knife training or straight up self defense? For the knife, any of the filipino martial arts systems are nasty with a blade. Joe Blow with a knife is bad news...being trained with a blade is d-a-n-g-e-r-o-u-s!!
For general self defense, i say Brazilian Jiu Jitsu...some folks will disagree, but I think the mechanics are just brilliant and nothing gets you up and running faster.
