In the Lord's Companion, I accidentally keep referring to Alluse as 'she' or 'he' in my drafts. At least it's good to know that I, too, am confused about my own character's gender. I just hope none of those errors have made it to publication.
I also noticed somewhat recently that I misspelt Genver's name in chapter 7, which is odd because that's the first time she's mentioned, and I spelt it wrong several times in the one chapter. Good thing she isn't mentioned again for another dozen chapters or so, but I've fixed the problem now.
In Darkest Challenges, I completely ignore the character's Bag of Holding where she stores all of her items and gear. There are countless scenes where it should be strapped to her armour or in her hands or something, but I just pretend it's not there until it needs to be. I can't remember why I chose to do this, but it's done. The entire premise of the story depends on the reader not noticing this detail. Please don't tell anyone.
EDIT: Also, I just noticed that this thread appears in the sidebar as, "When you know you fucked a minor..."