I've been doing martial arts off and on since I was 7. I started with Karate I don't remember aside from kicking some poor kid in the nuts on accident, then switched to Tae Kwon Do when I was 9 or 10 and took that to black belt by practicing off and on for about 7 years. After that, I switched to a specialized form of Karate developed by Al Case (you can read about him and his systems at
index) by studying under his former student (again, off and on) for about two years. I've been studying with Al Case himself for almost two months.
This is a multi-art system, starting with Karate. Al doesn't seem to belt-classify, but his former student had me at 2nd Brown Belt (that's roughly in the middle of the karate) when I left.
Another month, two at most, and I should be on to Monkey Boxing, which is a variant of Kung Fu.
I recommend Al's system (called Matrixing - NOT at all related to the movie) to any serious martial artist.