The rabbit-fur mice are the biggest hit at my house. Lucky plays with them pretty much exclusively, and likes to pick them up and carry them around in his mouth and announce that he's "caught" something. He also likes tennis balls, because they're fuzzy and he can wrap around them and dig his feet in. One of his favorite games is to swat small objects into the floor from a table or shelf, so we put the mice up where he can swat them off. It's hilarious XD.
Stinky rarely plays with anything, but I can sometimes get him to attack one of the mice, and sometimes he'll play with a ribbon on a stick. His absolute favorite thing to do is scratch on cardboard boxes, and if he's able to he likes to get inside them and scratch on the insides.
Until he got fat and lazy, James loved to play with those shiny crinkle balls, and to a lesser extent any kind of small, ball-shaped objects. He is also a fan of the mice.
Clark is the only one who plays with the ball-in-the-track gizmo. He also loves this feather-boa-on-a-stick toy, and will actually drag it around the house in his mouth when no one is playing with him.
Best cat toy ever! My cats used to play with those all the time. We had to stop dropping them in the floor when I got my dog though.