I dunno, I've seen a few that made me take my hand off my cock and really think.
Like the one where the guy's wife has a disease that's slowly turning her into a bug woman, and he's not just scared that the transformation will kill her, but that when she finally does die she'll be so inhuman he won't love her anymore. Then they bone, and he realizes that no matter what form she takes, they will always love each other.
Beautiful. Brought a tear to my eye.

To be honest, that's a deep analysis of the genre, very meta
Emphasis on deep.