most people in america die due to some heart related issue. statistics support this so i won't get into it. regarding this, cardio is the ONLY thing that will prevent this. in fact, too much weight lifting and power excercises and such can put a great deal of strain on the heart valves (unless done with exceptional technique) and therefore make the heart even weaker. running is by far the best full body(inner and outer) workout, but it can also be acknowledged as one of the most damaging to the joints as well (most notably the knees, without exceptional technique). so if you're too weak to run, then swimming is a really great option for getting a pretty well rounded workout for your body, as well as maintaining heart health, which is all too often neglected, especially in america.
i personally only do excercises that involve my body. i try to avoid weights at all costs. if you get enough into it, you can find that it's possible to work every muscle group in the body without any kind of weight or machine whatsoever. it's possible to gain weight using this method also (or lose it, depending on the way in which you do each excercise).
slow builds mass, fast tones mass