Your favorite "girl disguised as boy" / crossdressing books

I want to read more books where the FMC is disguised as a man for one reason or another, and the love interest believes the disguise, or at least isn't sure, and falls in love with "him".

The love interest can be a man or a woman, or both. The "FMC" can decide to go back to being a woman at the end, or not. But s/he should definitely present as a boy for the majority of the story.

I really love pirates and other adventurer types, but I'm open to different settings. Spice not needed, and maybe not very likely with this type of plot.

I'd also be interested in MMCs dressed as women, but I kinda doubt there's anything out there (short of unambiguously transgender stories).