We have 3 dogs, 2 of whom are quite large and love to play fetch.  Our rattie, Ripley, has been dying to get in on the game as well, but his little mouth can't quite get around a normal-sized ball without problems.  I have had to remove all tennis balls from the house because he about unhinged his jaw when his teeth got stuck in the fuzz when trying to pick one up!  So, I have been playing fetch with the big girls, but poor Rip has been left out unless he "deigns" to fetch a stuffed toy, which he seldom will as the girls aren't.

A couple days ago, I was in the pet store and they had just gotten in a new shipment of Cuz toys.  I was so excited!  Cuz makes toys that even our GSD (who can crush a tennis ball in one bite!) hasn't yet been able to destroy.  And they had them small enough for Rip!  They are made of heavy-duty rubber, but not quite as heavy to chew as the Kong.  The squeaker is the same as the one used in their very large toys, so there's no danger of Rip managing to remove it.  Because of the protusions, even the GSD is careful with it and we have been able to include everyone in fetch.  We have been having a lot of fun!

If anyone else has been having "ono!  I can't find a ball small enough or safe enough for mah rattie!" issues, take a look at the Cuz line.  Here's a link to a number of them listed on Amazon.com.  Size for Rip at 10lbs is, of course, small. (I got him the little evil red one in the main pic.): www.amazon.com/JW-Pet-Company-Nature-Assorted/dp/B000OXAFHQ/ref=pd_sim_k_3