The top exercise on my list for overall conditioning is no doubt sprints.  The second would have to be sled pushing or sled dragging.  Sled pushes and drags build lower strength and power and also incinerate fat because of the high power output and intensity of the movement.  You want sculpted and firm legs and abs?  Sleds utilize the entire posterior chain and core. They have very similar benefits of squatting and deadlifting, but less impact on the joints because of nature of the exercise.