Asana - the third limb of yoga

Asana is the third (out of eight) limb of yoga.
In the very old days Asana meant "to seat", probably  in meditation posture
With time it turned to mean a body posture, and then, the physical practice of yoga.

"Sthira sukham asanam" Poture should be steady and comfortable.
The Yoga Sutras of Patanjali, 2.46 Bryant's translation.

According the Scriptures Asana should be practiced because:
1.  It prepares the body to be able to stay in seating meditation posture for a long time.
2.  It creates "tapas", heat that purify body and mind.
3.  It loses all awareness of the sensation of the body. the mind can now be focused in meditation  without being distracted by the body.

What is your favourite Asana? What is your less favourite Asana? Why?