For me, cleaning.
I don't like doing it. I'm naturally the sort that'll leave the dirty dishes until I absolutely need a clean plate, don't like taking out the trash, etc. If I leave it be, my computer desk quickly becomes filled with wrappers and coffee cups. Plus my wife and I have a 3-year-old, two cats, and a puppy. Plus we work full time. So if I leave things for a day or two it quickly gets out of hand.
So once a week on my day off I put my son in daycare, get the house to myself. And I'll spend a few hours going through the place top to bottom, doing all the dishes, getting the clothes sorted, putting everything back in it's place, dusting vacuuming, etc. It's just nice to be able to sit down and relax in a clean house and not have all the housekeeping chores in the back of my head stressing me out.
My therapist says I have a tendency to view my house as a metaphor for my own state of being, they're kind of symbiotic. If I have a dirty house with a lot of things that need to get done, then I start feeling depressed and overwhelmed and stressed out. When I feel happy and relaxed, I also tend to have a nice clean house as a byproduct. For me, cleaning is just very theraqeutic (still don't like doing it though.)
When my son was first born, I took a year off to be a stay-at-home father (other things happened so that didn't end up being quite as long-term a proposition as we'd planned.) So I'm also kind of in the habit of keeping up with the house as just something I do, part of my responsibilities.