I have American Bobtails. And the females especially are excellent mousers. They even catch mice and bring them back to their litter to teach the kittens to mouse while they are young. I'm not real happy about momma bringing mice into the house for her babies to practice on, but she has never let any get away from them alive.
American Bobtails are a naturally occuring bred. For whatever reason they just started showing up without tails from time to time, mainly on farms. Now, they are a registered breed and can be very expensive.
I got my first two many years ago from an old poultry farmer. I just can't say enough about them. They act more like dogs than cats. And the males take excellent care of the kittens when mom is out hunting. I have even had males lose the hair around their teats from nursing the babies while mom was away. And these are big males.
Anyway, I love mine. I hope that with the breed now being registered and valuable that the brains and instinct doesn't get bred out of them in favor of good looks.