I bought 12 "Penn" decent quality (lots of bounce) ping-pong balls at
the local megastore. Most of them are on the floor. Also on the floor
are three of those "midnight madness" or whatever they are called
plastic balls with bells inside. We are getting a lot more use out of
the ping-pong balls. The cats enjoy batting them around, bouncing them
off of things. When they come near me, I kick or throw them. Almost zero
risk of hurting anything. They play with the ping-pong balls more than
they play with the bell balls.