It depends on the dog. I feel safe leaving my dogs with kongs and kong like items, but I've heard of some dogs that can destroy them. I would never ever leave my dogs with any type of rawhide, but then I don't really give them rawhide anymore. I also feel safe leaving them with those big knotted ropes. But then I've heard of dogs who dissect them and eat the strings.
So I guess I'm not a big help at all. Sorry.