I'm not personally much into anal-sex in my own sex-life, but watching porn anal is always my def. #1 choice - all positions looks better with the cock inside the ass rather in the pussy! I suppose it's because you get that perfect view of that sweet pink taco in a wild sex-scene without the cock blocking half the view but rather thrust in and out lil' pussy's good neighbour. Best of two worlds sort of speak.
My #1 favorite position is the anal piledriver - this is close second - especially when the girl's got her feet on the guys thighs (I'm no foot fetish-guy though so that's got nothing to do with it, just simply because you get that perfect leg-view at the same time) ALT. she's wearing heels, and then the guy should keep his legs more together and let the sexy "M" stand even taller that way.