My buns favorite toys are toilet paper tubes, paper egg cartons, Balls made out of grapevine, or wicker, Baskets made out of wicker, Grass mats, apple sticks.
Oh and I also just bought him a new toy, its taken a while for him to like it but now he loves it. Its a colorful plastic chain that I found in the bird section. I tied it to the edge of his cage and he digs at it all day long and tries to throw it around. He didn't like playing with it when it wasn't attached to the cage. I think now now that its stuck he spends all his time trying to remove it.