I’ll start:
One of my favorite chocolate bars is Twix. A typical pack contains two identical bars. A little while back they started selling packs that, while still containing two bars, claimed to contain “just left Twix” or “just right Twix”. The joke being, there’s no actual difference between a “left Twix” and a “right Twix”, so nothing has changed except the writing on the package.
Here’s the irrational part: Whenever possible, I buy Left Twix instead of Right Twix. For political reasons. 
Makes sense to me.
I check that the door is locked even though I know I locked it. Not totally OCD as I only check once. So far.
I read fortune cookies. They’re true, dammit! Though I do seem to get other people’s cookies by mistake pretty often.
Still worrying about small amounts of money.
Wear the same polo every Thursday during baseball season. That’s my last day of the work week.
Use a special coffee cup every Thursday, Friday, and Sunday. They date back to around 1998
”Thank you for your unwitting participation in the psychosocial experiments of Mars, Inc. For our next query, we’d like you to respond as to your preference for the red or blue M&M.”
Stranger
Try to explain things to the pets.
Worry if the lil’wrekker is driving carefully. ( she’s never been a reckless driver, she’s 19yo and lives at her college).
Fight with myself about being so agoraphobic. At this point it’s never gonna get better, but it could get alot worse.
Trying to compute the square root of two exactly. 
Sometimes I get a wild hair and drive crazy like the locals. There are no patrol cars monitoring traffic. I look at my speedometer out of sheer curiosity. It’s fun as hell, keeps you on your toes.
You know when you buy bulk food in a bag? I never put a knot in the bag, because the knot will make the bag weigh more.
In a thread from a few years ago, someone mentioned “toilet races,” as in flushing the toilet before you’re finished, with the goal of the final bowl-clearing event happening just as you finish peeing. Why do I keep doing this? There’s no point.
Do you find that often they contain advice instead of fortunes?
I don’t step on cracks in the sidewalk. Or lines (which are different from cracks. Lines are put there intentionally by the contractor - cracks develop due to tree roots or the heat/freeze cycle).
I’ve never found a fortune in one of those. I consider a fortune to be at least $100,000.
I regularly get angry at inanimate objects when they aren’t doing what I want them to do. I’ll put the remote control on a table, and then it falls off, and I know that I put it in the right place so it must be the fault of the control or the table.
Do lottery numbers count?
Winning lottery numbers do.
I’m glad I saw this, I was going to start a thread about it. When I’m watching a tv show or movie, and one of the actors has an accent, I always turn the volume up. It doesn’t make sense to me, but I do it, all the time.
Personify things.
Maybe it’s more of a deep seeded psychological thing that I’m willing to admit, but I have a lot of fun personifying inanimate objects.
For example, I have a little, potted plant at work. His name is Mitch and he’s grown a lot this past year! Good for Mitch.