What's the most petty/pointless/pedantic hill you're willing to die on?
For me, it may be that the toilet paper roll needs to have the open end away from the wall. I don't want to reach under the roll to take a piece! That's ludicrous!
That or my recent addiction to correcting people when they use "less" when they should use "fewer"
I converted my wife in the T-shirt thing when we were folding laundry together and I had a giant stack of shirts and she had to make several small stacks because hers kept falling over.