Why she's sexy: Pretty much any character played by Megan Fox has to be sexy. She could play a bag lady and that body would still look bangin'.
Why she's bad: The whole being-possessed-by-a-demon thing doesn't exactly put Jennifer in the whole Sunday school set. Notably, Jennifer stands out in the horror genre as one of the few genuinely sexy female killers. The only other one we could think of: Rebecca Gayheart in the slasher movie "Urban Legend."