How can I get agile, flexible and strong in a fun, dynamic way?

Pole dancing. I have a friend who takes classes and loves it. It takes a lot of strength to do the routines, and the classes aren't all hoochie-coochie. Not that pole dancing is necessarily a super power ("Stand aside, citizens! Pole Woman is here to save the day!") but you could toss it into your mix as a way to work out your legs, shoulders, arms, and core. Plus you could wear a Wonder Woman costume while doing it.

n-thing Aikido and Capoeira; Aikido might be easier to pick up depending on the quality of instructors available. Gymnastics and Parkour are the skills that you are asking for. Both kinda require extreme physical fitness; great strength/mass ratio, flexibility, and aerobic endurance. These traits will require strength training, movement training (yoga might be great), and boring stuff like sprinting/running/track&field. Jogging/swimming to lose weight and gain endurance, yoga to gain flexibility, gymnastics to learn about your body, freeweights to gain strength. Or maybe Western fencing? Epee, perhaps. Lots of sweating and quick movements. "Killing with the point lacks artistry, but don't let that hold your hand." There's no shortcut. Unless you join a hunter-gatherer society who're going to drop your ass if you don't contribute, you're going to have to suck it up and (make yourself!) work to get into shape. The key, I guess, is to choose to do something that you enjoy doing - with the side effect that it gets you really fit. Sailing... old-school sailing burns a ton of calories and works a lot of "sexy" muscles.

http://en.wikipedia.org/wiki/Slacklining A while ago, I did a http://www.metafilter.com/91763/The-Fundamentals-of-Bodyweight-Strength-Training-And-some-other-links-on-the-same-topic that you might find useful.

Parkour and gymnastics can be really tough on the joints, particularly if you are currently over weight (you said you are out of shape, which doesn't necessarily mean over weight). It is a young person's hobby. Something like aikido would be perfect. You learn to become really aware of your body and its position in space, which is essential to dodging bullets. Learning how to fall is even more important than knowing how to toss someone, aikido will teach you both. I also found it to be a lot of fun. Also, hang out around radioactive insects.

2nding Capoiera. There is a learning curve, but it will whip your butt into shape and teach you many new feats of skill and strength.

You may want to check out http://idoportal.blogspot.com/ http://www.youtube.com/watch?v=6_eTg6gMTE0 He has a bunch of training videos on http://www.youtube.com/user/portaldo#g/u.

Learn to box. Nothing quite like a stiff jab between the eyes to spur one's continued improvement.

dynamic, fun and required mental energy, with fitness a side-effect of working toward a goal This is exactly why I go to a rock-climbing gym regularly. It's enormous fun, there's a lot of problem-solving, development of discrete skills rather than just retracing identical perfected physical motions over and over, and the great workout I get is almost incidental to the fun I have.

I'm a fan of inline skating, myself. It only really works if you live near some nice bike paths, and you need to make an initial investment of money in equipment and time in learning how to do it. But it's a kick-a** workout and you feel like you're flying. I can do it for an hour-plus and not be bored in the slightest.