DH's invisibility cloak. For whatever reason, the kids forget that he exists when they want something. DD just climbed down, off DH's lap, then came to me with her empty cup asking for juice. A couple weeks ago when I was sicker than a dog, trying to sleep was impossible. The kids were coming to me wanting everything from lunch, to crayons, to help tying DS's shoes. You'd think they could remember Daddy exists after the 15th time I sent them to him, but no.
Also, running errands with the kids. DS had errands too, so he had to come. But Dh asked me to take baby as well. What would have been an hour, maybe an hour and a half trip by myself, or a 2.5 hour trip with DS turned into a 4 hour extravaganza.