The people behind the Hercules Hook claim that you can hang anything on a wall without worrying about finding a stud. Popular Mechanics put the hardcore hook to the test, as they are wont to do. The results were impressive. A 41-pound book bag hung from the hook with no problem. A 68-pound lawn mower would have been just fine as well, except the dry wall itself couldn't handle the pressure.
We recommend the Hercules Hook up to the point that you'd have to consider buying heavier-duty drywall to keep whatever crazy stuff you want to hang on your wall supported, you freaky home decorators, you.