It may not look like it, but this martial arts move is one serious abs toner—your obliques and abdominal wall muscles have to work during the entire exercise to balance your body while you lift and extend your leg.
How to do it: Stand with arms bent, hands in fists by your chin. Rotate your right heel in towards your body and shift weight to your right foot. Bend your left knee, flexing foot, and lift leg up to hip height, aiming right heel to the side. Extend your left leg out to the side, as if pushing something away from your body with your heel. Bend your knee back in (try not to lower leg in between repetitions if possible). That's one rep. Do up to 3 sets of 15 repetitions on each leg, switching sides after each set.
If this is too tough, try lowering your leg for the kick and/or holding onto a chair or wall with your right hand to help keep your balance.