Some of mine don't bother with chewing regularly, but when offered an antos chew (they're called Whimzees in the US, can be bought at Petco) they go crazy over it.
Mine also love walnut in shells, I drill a few holes in them so they can smell the nut inside. I also have a few robos that love apple chew sticks and will shred them to bits in a few days, but most of them don't really pay any mind to them. I guess some are just more picky than others.