I dance capoeira, and although it isn't full-bore cardio, you spend enough time in the right zones (over the course of an hour) for it to count. Plus, it's good for all-around strength training. I didn't start out with any extra weight, so I've put on a few pounds of muscle across all the major muscle groups.

I do judo. It definitely works. I have better cardio, I'm stronger, more flexible, thinner and more confident. And it helped and inspired me to lose even more weight and try out other sports as well (alongside judo). Having a good trainer, and a good group of colleagues, helps a lot.

Bujinkan (japanese budo, similar to jujitsu ) I've been in more than one school and the most recent puts a big emphasis on fitness, with fitness tests every few months. Depends on the teacher/dojo more than the art, I reckon.

I had a friend quit training with us for a couple months and he can no longer keep up. I lost at least 10lbs in the first six months of training.

Depends on how you train.