I highly recommend these "cat toys." They come in packs or 10 to 100 and a variety of colors. And best of all, when your cat is not playing with them, they double as something you can put your hair up with! Imagine that!
Moo, on the other hand, prefers real toys -- the bigger and more ridiculous, the better. Which is good, because those are more expensive, so they kind of even each other out.
What are your kitties' favorite toys? Do share!