I have to say, as a GM, I want the players to start with a concept and work from that. BUT I absolutely do not want them to start with a character from books or anime or some batshit crazy idea and expect me to beat the mechanics all out of shape to accommodate them.

I saw a post on another site (which shall not be named) where the player wanted to play a monk with eyes on the palms of his hands instead of on his face. He claimed it was for flavor but he also said he wanted to just be able to close his fists and ignore any negative effects from seeing something, such as a gorgon or basilisk. While I admire the creativity, I don’t have any interest in screwing up the playability for other characters and for myself.

When I’m a player I start with a role, then layer on something odd/quirky, then look at how I can implement it within the rules.