I'd like to start with my favorite of all: people who use "lesbian" as an adjective.
Let's be clear about this. I have no problem with gay-themed fiction or non-fiction. In fact, I read a lot of it in the fan fiction world. What I am referring to the case where the protagonist is something else, and the male author (because the author is always, always male in this case) feels the need to add that she is lesbian. There is the lesbian militant. The lesbian detective. The lesbian vampire. The lesbian psychic. The lesbian psychic detective. (I've seen it) Man, those lesbians are out there, doin' things, probably having sex at least once in the book I'm guessing, as we never request this kind of material. I'm sure there's a shower scene that wasn't totally necessary to the plot. Thanks, male author!
The greatest query letter ever would be about a militant lesbian psychic vampire who solves crimes. And by "greatest" I mean "worst."