Stories where sexuality is kinda ambiguous or fluid. The gender bender stories have some fantasy & comedy elements by default, while cross dressing stories are more slice-of-life. Some are just straight up SMUT/Hentai, but many stories also focus on gender identity with nuance. These kind of stories just have unique dynamics that I really enjoy reading about.
Note: I have a different list specifically for BL/Yaoi cus this one has both Female and Male MC.