Well-made natural-looking sitting poses for both genders. For women at least one where legs are together for tight skirts and long dresses, otherwise I'd go by personality/mood variations:

Cutesy, casual, femme fatale attitude, relaxed... you know, just different styles.

I'd expect at least five per gender, and couple poses -are- always a plus, of course.

For poses I don't honestly even care if it's animated or static, as long as the pose itself looks good and natural.

SonyaMarmurek: That's really helpful - I don't wear long dresses much so hadn't even thought about that. Thank you so much!

It's always been my bane in SL furniture, just poses where the skirts stretch/clip/vanish in ridiculous ways! Although when wearing minis or pants, the more relaxed ones are fun to lounge in.

I do have a (weak) preference for animated poses in chairs, and I agree with Sonya in everything she said.

I would also like to add that poses that take into account the existence of mesh/sculpted breasts (i.e. animations whose hands and arms won't get into the breasts) would be greatly appreciated.