My very favourite pairing is Severus/Harry, but I really like anything with Severus in it, be it slash or het. :3 I also enjoy a host of other pairings, from Ron/Lucius and Kingsley/Percy to Pansy/Neville and Ginny/Luna. XD I'm quite the pairing whore, to be honest. ^^°
But Harry/Draco just feels a bit... overdone, to me. My first experiences reading slash fics were Drarrys, but, well, perhaps it's a bit too mainstream for me. ;D It feels a bit too obvious and easy, and I miss the unabashed bastard-ness of Severus! ;D