My friend takes Taijutsu (which is the martial arts part of Ninjutsu, but the two aren't really the same). It's a lot of locks, body control, and quick strikes. The different forms are pretty varied, so if you get good at it, it's a very versatile art. The big downsides for someone your size (about my size, actually) would be that a lot of it is about controlling both your own body, and through that your opponents. Lots of movement, and the power to the motion is usually done through either up/down motion, or forward/back motion.
Similarly, TKD is all about up/down power. Muay Thai is roughly the same (though much more destructive). Sambo would work well for you, so would Krav Maga. But, if you're also looking for a style more on the "art" side than the "martial", I'd suggest Shotokan Karate (which is what I practice).
Most of the power comes from your hips, which will work well for someone who probably has very strong legs. It's an older style than Sambo or Krav Maga, so you get the more spiritual side of the training, as well as the self-discovery. It's a pretty well-balanced art, with a good focus on the quick and dirty side of combat, in addition to the more civilized kata and sparring.
I did forget to mention, though. The arts you seem to want to take are much more aggressive, and of the "hurt them before they can hurt you" mindset. If that's what you're interested in, Shotokan might not make much sense for you. It's a primarily defensive art, with more counters (similar to Aikido) than pure attacks
