..but they do love some simple pebbles, which are, fortunately, dirt-cheap (or pebble-cheap :) ) although a little messier to clean than the above alternatives. I think they'd like sand as well (I live in Uruguay and those pebbles are from Argentina, so I don't know what alternatives are in the U.S.).
"Yeah that's great and all but I've tried that. 3 litter boxes. All cleaned twice a day, and he still shits on the carpet 2 feet away from the box. Lid on, lid off, big sidewalls, different cat litter. I've tried it all. The little shit just likes shitting on carpet I guess. And putting the fear of god into him does nothing."