i love every shade of fic, but what drew me in was the sex because it had taken me so long (thirty years) to realise that there is something called slash and that i am not a pervert. well, or, maybe i am, but at least that i am not alone :D
tryfanstone's congress tripartite? is undeniably a pwp, but it's so skilfully written and so delicious, that i find it doesn't matter.(it has a fair bit of lucius/severus in the beginning though.)
i don't look for fics with character death or happy endings - if it's written in a way that appeals to me i'll read it and like it.
also i like to be surprised. and if i would only read fics with the same ending then it would be hard for me to be surprised. so if an author decides to kill one or both off, to separate them or to marry them - as long as it's a natural progression from the plot, i'll read it.
of course, i want to see snape happier, too, well, and treated fairer</a>, than in canon, where he basically gets to be beaten up, bullied, nearly killed, cut off by his only friend, misunderstood, probably even tortured, manipulated and then killed by a gigantic snake. i mean that's a bit much, really.
i am not very much into fics that feature a domestic harry who cooks and bakes, and fics where everyone is gay (remus is with sirius, and dean and seamus expect their third baby, and draco is bonded to blaise, etc., etc., ... )
i do have a weakness for pregnant!snape and animagus!snape and devour fics where snape is stuck in cat/scorpion whatever form and harry has to take care of him!