4. Patrick Troughton, the second Doctor. Let’s consider that at the time when Troughton took over, the whole Regeneration thing was just an experiment. It could have very easily failed and Troughton could have been the very last Doctor. Instead, he gracefully took over the role from the beloved William Hartnell and gave the role its characteristic quirkiness. At the same time, Troughton’s Doctor was definitely a dangerous man to mess with. And who doesn’t love a complex character, right? Unfortunately a lot of Troughton's episodes have been lost, but the BBC recently released a remastered version of one classic.

Check out the trailer below.