We've found that my cat's favorite toy in the entire world is a regular plastic drinking straw. On the bright side, his toys are REALLY cheap, or free, basically, if I bring extras home when I go out for fast food. He'll even fetch them if they're thrown for him, and will come back and drop them at your feet to throw again... after mauling your hand a little.
There are only two negatives... my house is full of chewed on straws. I tuck into bed at night and find them buried in my sheets. And then, there's this: