4. Jamie McCrimmon (1966-1969)
Played by Frazer Hines, he holds the distinction of being in more episodes of Doctor Who than any other companion, and more episodes than some of the Doctor's themselves! In the narrative, Jamie McCrimmon is from Scotland in the 18th century, and traveled entirely with the second Doctor. He faced off against Daleks, Cybermen, Time Lords, Ice Warriors, the Yeti, and even a unicorn. And yet, he never lost his cool throughout those adventures. Honorable mention for "Best Companion" goes to Victoria Waterfield, seen in the above pic with Jamie. Tragically, due to the BBC scrapping some of the older episodes, there's only one story in its entirety that features her. Fortunately, it's Tomb of the Cybermen, which is absolutely awesome. If you haven't yet seen it, go watch it. Right now. You'll be doing yourself a favor.