Mine are mostly food-related.
I cannot stand to have one food touch another. As a child, I convinced my mother to peel my baked potatoes for me; she refused to after she noticed that I ate both the potato and the skin, just not together. After many years, I can tolerate things like beef stew, but I still separate out each little food chunk, and eat the potatoes first, then the carrots, then the beef.
I eat one item at a time, starting with whatever I like the best. That way, in case I die before the end of the meal, I’ve not filled up on something I like less and missed out on my favorite food.
If at all possible, I use a clean utensil for each different food item. Clean fork for the mashed potatoes, another one for the peas, and so on. At other people’s houses and restaurants, I just deal with it, but at home, I go through a LOT of silverware.
Sandwiches must have the exact same proportions in each bite. Heaven forbid there be more peanut butter than jelly on one corner! The cheese better exactly cover the burger, because if I find a bite with burger and no cheese, or cheese and no burger, it bothers me.
I eat my M&Ms in rotating color order, so no color feels neglected. Ditto with SweetTarts and other colored candies.
Yeah, I have some food issues.
And some others:
My alarm clock must be set to a round number. I can’t sleep if the alarm is set to 6:02 rather than 6:00. Even 6:15 bugs me, and I’ll go for either 6:00 or 6:30 to avoid it.
I am extremely methodical in the way I get dressed. Make-up goes on first, so I don’t get any on my clothes. Then underpants, deodorant, bra (just to make sure I don’t get any deodorant on the bra), left sock, right sock, pants, take towel off hair, shirt. Shoes don’t go on until after hair is all done, so I don’t get any hair spray film on my shoes. If I change this routine in any way, I don’t feel quite dressed, and it annoys me all day.
I once demanded a new phone at work because my phone cord was all kinked up, and after three months of constant fiddling with it, I couldn’t get it to stay unkinked. Drove me batty.
My upstairs hall light has two switches, one at each end of the hallway. I can’t stand it that one switch is always in the wrong position (up when the light is off, for example), so I’ve compromised by making sure that whichever switch is closest to me is in the correct position. That way, if I walk out of the bedroom in the middle of the night, that switch will be right. This takes more effort than one might imagine.