That "ass pose" is a definate winner but my favorite pose is where a girl pulls her knees up behind her shoulders and her box is totally exposed. Kim Chambers has made that her signature pose and it rocks.
One of the girls to display that pose is Taylor Rain.
I have to say, I realy hate that she turns me on, but sadly she's realy good at what she does. It's good for my mental health that she has retired.