Scrubbing the tub/shower. We have hard water (our softener is so old, just doesn't do the job anymore so we are planning to get a new one after the holidays) and the tub/showers get dirty fast. I just hate scrubbing them.
Second least favorite would be dusting. Sometimes I just dust the main tables and the TV area and don't bother with some of the shelves every single time. I think I have too much "stuff" and I get tired of having to take it all off the tables/shelves, dust, and then put everything back.