The reverse lunge with a twist works your legs and obliques. 

Reverse lunge with a twist form cue:

Hold a medicine ball or dumbbell and stand with your legs hip width apart. Take a big step back to come into a lunge position. Watch your alignment and make sure your front knee is stacked over your front ankle, and your chest is lifted with a tight core. Twist your body towards the front knee, then straighten back out and step the back leg in to start position. Repeat to the other side.

Head back to the form cue library here.