Rex: his chunk of a 'chinchilla cookie', mint, rolled oats, and his various types of wood, especially willow, and his newer favorite is loofah. When he was on the unhealthy streak, his favorite was banana chips D;
Penelope: Alfalfa hay, oats, she seems to like the bitty bagels, apple sticks, grapevine, and occasionally rose hips, but if you feed her a couple one month you gotta wait two until she's ready for some more. However her most definite favorite is any kind of flower that is okay for them to eat, meaning rose buds, hibiscus, dandelion we got a sample pack with some of those in it and she went ballistic.
Manami, Allora, and Habiki: REALLY enjay apple wood, don't really like the other stuff that is on Penelope's wood toy, and they like loofah, and hay. But I suppose that is expected. :]
They've never tried pumice, just for the simple fact I've been cheap and haven't ordered anything I wasn't sure they would like. They've also never had shreddies, they'll eat cheerio's but won't necessarily come begging back for more, unless if it's the grain kind.
Sorry, I always tend to write a lot.