Hurts like hell --> No Pain No Gain Fat Burning Ab Exercises. Burn fat and slim down while toning up your abs and strengthening your core. Repeat the circuit once or twice more. Click the image to see the moves in GIF form.
Ballet Abs - I don't remember doing any of these separately (except for crunches) when I use to dance. I got my "ballet abs" by holding it in during class for 10 years; however, these exercises are great for anyone.
Six Pack Abs Core Strength at Home Workout Pack for Men and Women