My first foray into +Jonathan Linneman's Light City is live on OneBookShelf. The Super-Pet is designed to be used along side The Brawler, The Elemental, and whatever other great classes are created for Light City. You can grab The Super-Pet here for free. The pdf contains the complete Swords & Wizardry Light class and a sample max-level character, Whiz the Falcon.
In some ways I feel the Super-Pet's abilities and stats may be a bit too good, but considering the roleplaying complications and such of playing an intelligent animal in modern society, I felt they should get a bit of extra oomph.