Like @fireinthepriory, I have to eat M&Ms, Skittles, Reese’s Pieces, jelly beans, etc., two at a time of the same color. One on each side of my mouth. And I have to finish off on an odd number. I can’t eat two sets of two or four sets of two. It has to be three or five (or more, but you get the point).
Also, when I take a bite of food, I then bite that in half and chew with half on each side of my mouth. I guess I like symmetry, too.
The volume on my TV/stereo/computer/CD player/etc. has to be on an odd number. If it has bars and no numbers, it has to be an odd number of bars.
While I’m typing, if I want to indicate that a word would be drawn out if I were speaking (I looooove pie!) the repeated letter has to be repeated an odd number of times. If the part of the word being drawn out is a double letter (Pie is gooooooooood!) it has to be an even number because in my mind it’s actually the odd number twice. An odd number in that case would make it asymmetrical and unacceptable.
When I do movie reviews, I have to do them in groups of three, five or six. One is too short for its own post, and two and four are even and unacceptable. Six is okay because my mind sees it as sets of three.
Obviously, my major thing is even vs. odd numbers. I don’t have a problem with two, and I’m not exactly sure why. And even numbers that end in zero are okay, too, because my mind categorizes them as “divisible by five” rather than “even.”
@Likeradar: I do that, too, but… on purpose. It’s because I spend so much of my free time doing puzzles and mind exercises. So I’m constantly listening to/looking at the words in the world around me and making things into abbreviation puzzles or anagrams (my favorite) or just counting syllables. It’s not an uncontrollable OCD thing, though. I’m just weird. :D