The answer to the "When opportunities arise around the house, which lens do you grab?" question for me is often whichever lens(es) I happen to be evaluating at the time. Some lenses are more easily pressed into general purpose use than others, largely due the focal length(s). Fortunately, 35mm focal length-containing lenses have been very popular lately and that focal length is great for general purpose use.
Especially great was when I was putting the Canon EF 35mm f/1.4L II USM Lens through its evaluation. Not only does this lens have the right focal length, but it also has a wide aperture, ideal for those around-the-house needs and often ready to capture high quality images without any additional lighting needed. That this lens has such great image quality at that f/1.4 max aperture is especially great.
On this day, Brittany came home tired and took a moment to relax with the dog that is of course tired and relaxing most of the time. My currently-mounted lens was the 35 L II and it allowed me to snap a few cute pictures using only ambient window light.