As a bachelor/roomate, I will say that other people's eating.... styles are also a cause for concern for me. but, I've got little habits which surely annoy my roomates. So, i'm trying to slowly get a few habits away from both of them. First of all, I'm the only one who cooks Meals. Although they both have their fair share of pasta/bacon&eggs. So we all share crockery. Only problem is, one roomate believes that leaving egg residue on the frying pan adds to the taste next time you use it... In a week. Now, I don't like egg anyway. So I find that a little disgusting. And the other, on the other end of the scale, doesn't like leaving things in pans. So he plans to clean it, by first leaving some water in it, y'know, to soak, loosen it all up. That's fine, and good cleaning practice. Unfortunately, he forgets about it. And seeing as they both cook on the odd occasion, it can stay there for a very long time.
Now, my major way to fix this, is just to make casual jokes- ranging from 'I think you forgot to clean your pot, last I checked, it was trying to escape through the window', to "Dude, Either clean that damn thing, or start feeding it twice a day."
Edit: Got my roomate to play Amnesia: The Dark Descent.
After passing the cellar (I think), he stopped playing and went back to WoW. A few days later, I'm talking to a mate, and say 'Yeah, ben was so scared he stopped playing it'. At which point said ben yells at me 'When do I get the pistol? What is the point of me playing a game where I get scared, run, and hide, get scared, run, and hide all the time?'
I'm gonna kill him.