The first one I remember is that any pressure I felt had to be symmetrical over my body, so if my hand touched something, I'd have to touch something (the same thing, preferably) with my other hand. Both sides had to feel the same, including my back, so sitting down was tricky; I'd have to keep moving around until the pressure felt the same all over it. The number of times and order in which I touched something mattered too. A touch with one hand demanded a touch with the other, but then the fact that I'd gone from left to right wasn't right either. I had to go from right to left in the same way to balance out the numbers. That also didn't work, because those four actions had to be repeated in reverse: right-left, then left-right. This would continue until I lost count.
I gave that up at about age eight, and instead began to hide my skin form the sun at all costs, with clothing over my head in the car and standing in any shade available, however inconvenient.
My general health-consciousness was unhealthy for a while, ironically.
I'm not sure whether this would be more phobic than obsessive-compulsive, but I try not to sit in front of people while they're eating, because I can't bear the idea of them spitting at me. I avoid looking at drinks because people don't wipe off the marks their mouths make on them as I always do. I'm very, very easily disgusted by certain things, yet I'm not squeamish about blood and actually like the smell of fertilisers. :?
