I don't care if it's a human, a car, a planet, or whatever. If there's something you always forget to draw that should be obvious, feel free to share it here.
For me when it comes to humans, I often forget to draw the nose, and especially lately ears, Even in my finished and publicized comic, you may see characters who are missing them. (While I making this thread I discovered some new ones in fact)
A more specific example is whenever I'm drawing Kirby, (as in the videogame character) I always forget until the very end to add the cheeks.