OMG It's really comforting knowing I'm not crazy. My Quirks:

I MUST(!!!) count stairs that I'm climbing in patterns of eight. And rotations of my bike's pedals.

In the shower, I have to wash everything twice, otherwise I'm never clean enough... even if I were to scrub 'till I were sore the first time around.

Tap the dashboard of any car I'm passenger in twice when going through any light that turns yellow.

Even if I know I locked the door, after getting into bed at night, I MUST get out of bed, check, go to bed, then get out and check a second time.

I'm noticing a pattern of numbers that I never really thought of before... all even numbers, and I have no choice in the matter. I won't feel right unless I do it in the prescribed number, but for some reason when it's left up to personal choice I ALWAYS pick odd numbers like 3, 9, or 27.