Checking that my front door + security door is locked before i leave, most times i'll leave... return a few times (within 5 minutes), just to make sure that it is locked. Other times i'll return as i NEED to see whether or not i shut the door (as i can't remember if it clicked when it shut etc).
I dislike dust, my main lounge room area needs to be dusted before i start playing video games or watching dvds. This is mainly so i don't get dust in my game console, dvd player..... or have dust make contact with the dvds / game discs.
I see what other posters have said about not touching door handles, i do that aswell - not to a large extent. If there's no handle, i'll happily use my body weight to open the door. I've also used my elbows to turn light switches on & off (imagination makes it look worse than it is, i actually started doing it as a form of 'exercise').
I used to be an excessive hand washer, previously it was the standard wash before/after meals, visits to the toilet, taking out the garbage etc. Something happened to me a few years ago (had to fix a blocked toilet), i wasn't the same person after it. Had a bit of germ paranoia, that in some aspects still exists (such as the touching door handles thing). Over the last few years i've reduced the amount of times i wash them per day.