i'm sure other OCD people do this, but if i turn on/off a light switch, and it doesn't feel right, i have to turn it back off/on and do it again until it feels right, takes several tries sometimes (but i can control it enough that i'm not standing there for 5 minutes doing it)
if i try to open a locked door and it gets part of the way until you get to the click when you realize it's locked, it makes my entire body uncomfortable until i can find an unlocked door handle to open
i need to count to 10 before i can start a set of anything, otherwise i'll never lift anything ever. i have to tell myself okay you can stand here not doing anything til you get to 10, but as soon as you hit 10 you're starting that first rep
when i'm driving a car i imagine driving off bridges or into a tree or something like that relatively often and sometimes really have to fight to not do that, though i don't think i've ever been that close
i like thinking about large quantities of people dying. I'd never actually kill anyone, but I find natural disasters/terrorist attacks like that and how people react to it absolutely fascinating. Sometimes I find myself almost pulling for the death toll to rise, even though I could never live with myself actually killing someone. If I could control stuff that happens I'd shoot a huge meteor at the Earth and have it kill most of the people, just to see how everyone reacts before/during, and how the survivors manage to make it, then rewind time to before it happened so everyone was actually okay.
when i was in about 3rd grade i went through a couple year phase where i could only yawn if i grabbed the little floppy part of my ear. weirdest thing, took me forever to grow out of that one