Someone who uses their OCD instincts to complete almost every task they do. An OC Douche will not walk away from a task a until it is set up "perfectly" even if it is not necessary to complete the principle part of the task.
You spent three hours stacking all those books in size order. You are such an OC Douche.
Don't go reorganizing the closet. It's a little messy but everything's where it should be and it doesn't need further work. Don't be such an OC Douche.