I've always thought a miniature cow would be the coolest thing to invent. 

We've got teacup pocket-dogs and itty-bitty kitties, miniature horses, relatively smaller potbelly pigs - all who can live in our homes as our beloved pets.  I even read an article recently about a blind woman who used a specially trained mini horse as a service animal since she's Muslim and they don't keep dogs. 

But mini cows...that'd be really cool.