I’m going to go with dusting and scrubbing the tub.
(Dusting is easy. IDK why I don’t do it more often.)
I dust weekly - tho there are certainly some things that don’t get dusted that frequently, such as baseboards and ceiling fans.
I’ll offer washing windows/sills. We do it 1 - at most 2x/year, spring and fall. But it is a big job (even with tilt-in windows) and it seems like the day after you do them, it rains, and looks as bad as before.
As someone that cleaned houses for 19 years I’ll go with literally anything to do with the master suite. The master bedroom and bath aren’t places that company visits and is the most neglected area of most houses in my experience. It’s the last to get cleaned, painted, furniture, etc.
My husband feels very strongly about dusting. And he doesn’t mean Swiffer-dusting, he likes Pledge spray or something similar to be used.
I don’t care much about dust, but I’m very focused on floors and baseboards. When I’m vacuuming, I’ll swipe over the furniture with the attachment. Unfortunately, it leaves those tell-tale marks, so he knows I didn’t “really” dust. 
duplicate
In my house, it’s dusting and windows. I do a half-assed dusting job once in a while. A thorough dusting when we have a get-together. Windows get done when I can’t stand looking at them anymore, maybe once a year. It seems like such a waste of time. It doesn’t last more than a week, sometimes less.
Bathrooms, including tubs, are cleaned thoroughly every week.
Cleaning the crud out of the rain gutters. I do it annually, a task I hate, but it seems not many others do…at all. From some of my observations, some people have quite the weed garden or emerging forest of saplings growing in the finest of soil in their gutters. I should say, their sagging gutters.