The Third incarnation of the Doctor had three main on-screen companions, Jo, Liz and Sarah (although I'm counting Sarah with the Fourth Doctor for this poll!) He also had an army of supporting characters who became companions, including the hardy perennial Brigadier Alastair Gordon Lethbridge-Stewart.

On radio he enjoyed the company of one Jeremy Fitzoliver, played by Richard Pearce. In comic strips he was joined by a selection of deeply, deeply weird characters who generally only stayed for one story, although both Sarah and Jo joined him for a time. He even had on-stage companions in the form of Crystal, Jason and Zog who joined him for The Ultimate Adventure.

Finally there was his ultimate companion - The Master. But most people seem to think of him as a villain, so we'll let that one slip.

But who do you think was best? Choose!