For my outer waist, I enjoy heavy, weighted Roman chair sit-ups followed by hanging leg swings. Be sure to attack the hip flexors as well as the abdominals. Blows from the medicine ball from all angles are used to toughen the obliques. One handed deadlifts are excellent for strengthening the obliques if used suitcase style. Side raises and side bends work as well if done heavy enough.
Isometric contractions complete the workout.
Finally, nothing compares with dragging logs, old tires and trucks for giving a rugged appearance to the mid-section. Since the trunk is kept rigid, the entire frame is worked. It is essential to maintain the flora of the gut and to ensure that this flora is resilliant. Periodic consumption of dirty food and water will clear out the weaker bacteria by introducing more tenacious alien strains. These bugs will temporarily induce weakness, vomiting, and a loose stool in the host, thinnining out the common bacterial population and leaving room for the genetically superior strains.