bones and ice cubes
With regard to feeding the disposal bones, I've fed mine chicken bones, smallish pork chop bones, and occasionally rib bones. Yes you may have to cover the disposers mouth when grinding bones, I have an ISE PRO77 model, and I get bone schrapnel sometimes.
Steak bones and larger bones no. Too large
The bone pieces will scour the disposal an pipes very well.
Ice cubes: Will also clean and freshen a disposal, what I do is drop a handfull of cubes down and hit the switch, without the water running. when I can see the ice has been chewed to snow, I stopper the drain and run 2-3 inches of water in the sink, then remove the stopper and let the water run thru the disposal.