Since I've recently proclaimed this as my nemesis pose, I think it's only fair to explore Parsva Dhanurasana (Side Bow Pose) a little more deeply in the spirit of equal regard.
Parsva Dhanurasana is a strong asymmetrical backbend that strengthens the spinal extensors and quadriceps as it stretches the psoas and pectoralis. Even though it appears that both sides of the body are aligned alike, the muscular actions required to create this shape while lying on one's side are not symmetrical. The top leg must be used more strongly to pull the body open, toning the quadriceps. The more the body opens with this action, the more the psoas of the bottom leg is stretched.