Technically, you can. It just has to be made completely of foam and have a cloth cover. AKA a rock. You can make a rock look like anything if you want to put the effort into it.
Einherjar actually had/has a legit throwing axe rule. It did blue damage to whatever damage area that it hit. I don't honestly know if the rule is still around because as Ravus said; there haven't been any out for over a year or two now.
It was silly, but it kind of put something else into the game that was a fun twist.