Nikolai Tesla and his OCD

Tesla was very OCD. And that doesn't just mean he washed his hands more often than Lady Macbeth. He had an obsession with the number 3 to an almost frightening extent. Whenever he entered a building, he first had to circle the blocks 3 times clockwise, he only stayed in a hotel room if the room number was divisible by 3, and he always used exactly 9 napkins, which he kept in three stacks of three, and spent many of his meals calculating the volume of his food before eating it. He also loved pigeons to the point that he would import special seeds for feeding them in the park, and would sometimes capture them live and take them back to his apartment with him.

He hated jewelry (especially pearls, earrings, and pearl earrings), refused to touch anything with any amount of dust on it, and was terrified of anything round and/or metal. Of course that last one could just be a healthy reaction to working in a lab where most of the round, metal objects would fry you on contact.