Easily the hardest thing on a human for me to draw. Well... Actually, maybe it's feet. But I don't NEED to draw those as often. Now I am so sure there's a hundred different places I could go to find all the references I need. But I can't find anything on my own. What I've come to realize is that I can google these things for hours on end and come up with nothing. But one post on ConceptArt will leave me with an inexhaustible supply of awesome.
So how about it? I need fairly diverse and dynamic poses. Hands that are holding things, hands that are foreshortening, hands that pointing at folk. I absolutely cannot rely on my left hand to hold the exact same pose for the amount of time that I need to draw it.