me likes.
I'd divide my answer up into the following categories:
For a beginner who needs...
...to learn balance & improve strength
Tae Kwon Do
...health training (flexibility/strength)
yoga or Ti Chi or Qigung
...to learn self defense
American Kempo or Judo
for a person in fair shape who needs...
...to improve balance
TKD or Hap Ki Do & yoga or Ti Chi
...health training
yoga & qigung
...strength training
at this level, pretty much any popular Martial art will do
... to learn self defense
Jeet Kun Do, American Kempo, Judo, Akido (in that order)
for an advanced person who needs...
...to improve balance
yoga & Ti Chi, Bagua
...health training
yoga, Ti Chi, qigung
...strength training
Wu Shu or general Traditional Kung Fu, Bagua
...to learn self defense
Jeet Kun Do, Dim Mak, Kempo, Ninjitsu, weapon styles, gun training(I don't like guns, but it's still good to know how they work)
very advanced:
...general
Ti Chi, Bagua, Five animals Kung Fu, Kung Fu weapons, Kendo
...self defense
alot of the world military hand-to hand, above black belt level Kempo, traditional Karate-do, Aki-jitsu
in case you can't tell, I think the internal styles are important
anyone disagree w/ the above? have you tried a style which would fit better? The above is only stuff I've tried, I'm sure that there are other really good arts which I have no knowledge of. for example, I keep hearing about Brazillain martial arts as well as Hawaiian Martial arts, but I don't know much about them. Wing Chun either for that matter, nor Jiujistu or even Tae Bo

I wouldn't know where to add them to the list above.
My personal favorites are: Dim Mak, Drunken Monkey Kung Fu, Ti Chi, and American Kempo