- size differences: whether it's fairy v human or human v giant, a major size difference is very interesting to me. When just one digit is the size of a limb to the other being, it opens up a LOT of new possibilities.
One thing i would like to see more often is the smaller characters being the hostile ones, kind of like in the original stories of faeries.

- inhuman/human pairings: this ranges from the standard monstergirl trope all the way to things like horror creatures, actual animals, and robots.

- amputation: i like it in general, but i favor it when the amputations aren't symmetrical. There's something about destroying the symmetry of a healthy body that really adds to it.

- male rape: i find it slightly distasteful when it happens to a female, especially in a guro scene because it's pretty much expected at that point. But then again, rape is much more humiliating to a male because of this fact. A male isn't going to expect it the way a female would.