I have a black belt in Shotokan karate and used to be an instructor for a university club, and then occasionally for a club local to me.
I also have a black belt in a style of karate called Phoenix, which no one has ever heard of because there were only ever two clubs in the world... One in Paris and one in Weston-super-Mare (where I used to live). Neither club exists any more.
I've also done jujitsu, tae kwon do and shorinji kempo.
I'd rate jujitsu and kempo as good real combat martial arts. Karate is great for technique, fitness and discipline with approximately a 50:50 split between punching and kicks. Tae kwon do is much more heavily biased towards kicking, but technique is generally lacking. Before you all jump down my throat about the flagrant sweeping statement about tae kwon do, I should point out that it doesn't really matter what martial art you do... If you have a good instructor, you will generally be a good student. It just so happens that tae kwon do instructors *tend* to not place much emphasis on technique!
I don't do any martial arts any more because the pull of the sofa is much stronger.