Pecan loves walnuts (contrary to his name). I give him one and he will work all night on opening it. I can wake up in the morning with him prancing triumphantly around the empty shell.
Mine all love pecans, corriander, most fruit, porridge oats soaked in water, carrots, broccli, sunflower seeds, pumpkin seeds in fact most seeds that I have offered them.
Cheese is a major yummy for them but I only give it occasionally as it has loads of salt in.