One of my funny little quirks relates to email sorting. I keep emails with a "to do" sort of thing in my inbox: They need a reply, or have information that's relevant to a current project or I'm saving them to read when I have enough attention. Everything I'm done with gets sorted into folders by sender, if the sender is someone with whom I exchange enough email that s/he gets hir own folder. If not, it goes into an "etc" folder, or a "web" folder (these are people who respond to my web page). I have a few topic specific folders: "mosaic" and "poly" and "poetry" and "humor" are some of them. That's all normal, more or less, I think.
Here's the quirk: male friends who are in a partnership with a female for whom I have a folder get filed under her folder. This applies to ex-boyfriends, too, and, most amusingly, resulted in a friend's wedding announcement (the wedding is to someone else) ending up in the folder of mail I have under his ex-gf's name. This is completely intuitive to me, which is why it works, but it has confused at least one person immensely. :)