I have had several people ask this-and no it was not because they want a belly like mine 
People who understand strength training know all your strength starts in your center. The Core, the hips, the lower back-that is what determines your total possible horsepower. Core training is the only thing i consider more important than grip training when it comes to strength.
My personal training is nothing like what you will find in your local bookstores fitness section. I think this training must be constructed of heavy, compound movements that train the body to move as one unit. There are 5 primary drills i use, and 3 secondary drills.
1) The deadlift. I pull 95% of my deads with a close conventional stance. hips low and chest high. to connect the leg drive to the hip drive to the torso i need to flare my lats very hard and brace my abs. My abs are often the most tired after a heavy deadlifting session.
2) The suitcase deadlift. Great drill for the grip and the sides. No muscle will go unchallenged by this exercise. Take a long bar and place it to your side. Deadlift it as if your picking up a suit case or something like that. It is NOT a side bend.
3) Heavy kettlebell snatching. The kettlebell snatch works the abs very very hard. It also works the grip very hard. So for me it is a perfect drill.
4) The zercher pull. I consider this a separate workout from my deadlifting days. The zercher takes elements from a squat, a deadlift, a support feat and some round back lifting.
5) Windmills and Get ups. I do this drill together, i do a get up off the floor, than do a windmill, than go back to the floor.
My secondardy drills all come from the strongman side of the house.
1) Horseshoe bending. Tremendous cross body tension from this. Weak abs will rob a man of his potential here more than any other steel bending feat.
2) Steel Scrolling. Often i find myself in ackward positions, and a strong core is what allows me to find and make space for the next coil or turn.
3) Unbraced short bending. Learning to pressurize and brace the abs during short bends will make your core very strong.
Now there are about a thousand other great ab drills, and you can find them all right here
Combat core will give you everything. Smitty put the whole farm up on this one. It has been Diesels best selling product, and there is a reason for it. Athletes across America are finding out that core training does not have to be boring, light weight or the same old tried and failed crunches and side bends.
So to quote Forest Gump–”Thats all i have to say about that…”