Oooo! I just stumbled on this topic by accident and it sums up my family and me perfectly. We're all quirky!
Firstly, my dear Hunn must - I repeat: MUST - drop things exactly where he last finished using them in the expectation that when he next sees them, they will inspire him to finish whatever it was he was doing with them in the first instance. Now, that might sound a bit far-fetched, but my dear Hunn has been officially diagnosed with adult ADHD and a thing called OCPD, both of which can have this little quirk as symptoms. What fun!
My daughter will turn around through 360º so that she can touch or use a thing with her right hand first. If her left hand touches something first, then she has to wipe the thing and then turn her whole body around so the right hand touches it. She has been doing this since she was four and she's now twenty-two. There are other things she does as well (for example, she MUST tap the nearest wooden thing three times every time she hears someone inhale or sigh sharply), but I won't list them. They go on forever. Dear daughter has only a diagnosis of ADHD so far: she just has her 'little ways' and that's OK.
My son has a walloping number of diagnoses, beginning with Asperger's, OCD, Tourette's, GORD and etcetera. He's probably the sanest of us all, though. He went through a period where he would have to wash his hands until they bled, but thankfully that's over now. Later, he had a thing where he was obliged to pray before entering a doorway, but (also thankfully) that's gone also. Well, mostly. When he gets excited, my son feels compelled to flap his hands. Now, I don't mean just flapping as if to indicate a seagull flying peacefully into the distance. O no! I mean flapping so hard I fear his hands might fly off from his wrists! I kid you not! And he's doing it right now as he plays 'Assassin's Creed' beside me. He's up to a difficult bit and so the need to flap is really overwhelming right at this point. It doesn't bother me because I've lived with ASD (autism spectrum disorders) since he was born. However, it does cause various things to 'walk' off shelves from time to time. Once, a small anvil I use for leatherwork 'walked' off the shelf because of Matt's flapping and landed in my lap. I can't TELL you how glad I was that it hadn't landed in my left cerebral hemisphere!
Me. Well. As the mother of both these kids, I have my own set of 'little quirks' too. The one I'm willing to share today is that if I have to take a tablet from a blister pack, I absolutely HAVE to peel off every last scrap of the alumininum foil backing on the pack. This might sound simple enough, but it's not. That stuff is stuck so firmly to the package that I've worn my fingernails down to the elbows trying to lift off the tiniest corner so I can peel fragments of foil away from the package. It's not so crucial while there are still tablets left in the pack: I'm allowed to keep trying until the last tablet comes out. If there's still foil left on the pack, I might spend quite a while teasing and picking at it to get the desired result. It's becoming annoying, so very soon I'll do the exercise and 'allow' myself to stop that little habit. But not quite yet...