Four (Tom Baker) was the Doctor when I was a kid, and he kind of defined Doctor Who for me. I have to say now that Ten (David Tennant) is my all-time favourite Doctor.
God, I’ve never heard anyone call Three a favourite, @Zaku! What a misogynist ass he was!
The companions are a tough choice… in the ‘olden times’, I probably liked Romana and Leela best. From the new series, Donna Noble and Amy Pond. I also liked Rory quite a lot when he wasn’t in a full daze. I feel like people think of him as being Amy’s companion, which isn’t entirely fair.
And I liked the concept of River Song. She was a brilliant idea, but I didn’t much care for her as a person. I know a lot of people love Alex Kingston, but I think she was miscast in that role.