Here is a list of some hobbies that can get you into some serious shape! Some of them are obvious while some of them, not so much.

Sports

This one is pretty obvious, so I will lump all sports into this category and not it into individual sports. The main reason sports are so good is because you generally get a full body workout. Very rarely does a sport only require the use of a couple specific muscle groups. You also get an amazing cardio and core workout from most sports!

Handstands (Walking on hands)

Holy crap is this one awesome. Learning to walk on your hands is not only incredibly fun, but it is also incredibly hard. This one can take quite a long time to learn how to do just because your body is not use to it. If you get really good at handstands, you can start using them to do workouts by doing push-ups while doing your handstand. Also walking on your hands is great for increasing arm strength.

Dancing

Dancing is great for cardio and certain types of dancing can really give you a workout; break dancing in particular. Also, you know there are times where you will need to dance at some point in your life (weddings, parties, clubs, etc ...) Learning how to dance can really give you a confidence boost in these situations.

Diving

I am categorizing swimming as a sport but putting diving into its own category. I am also not talking about just jumping into the water and doing a pencil dive. Try doing some tricks and being acrobatic. Sure you might fall and mess up, but you will have fun doing it. When you are in the air all of your muscles are flexed as you prepare for your dive. Whether you realize it or not, you are getting a major workout in every time you div into the water.