7. Lynda (Bad Wold/Parting of the Ways)
Right, I don't care that it was sign-posted about a mile and a half away that Lynda was obviously going to die and be the person the Doctor couldn't protect. I still think she would have made a great companion. Coming from this odd, futuristic society that's been held back intellectually would have been an interesting angle to play with the character. Unfortunately, Rose would have gotten her back up at the new blonde who'd be coming along in the TARDIS, so ultimately it wouldn't have worked without some major rewrites. I just get so tired of almost all of the New Series companions being 21st century women. Lynda, on the other hand, is close enough to the traditional companion template that people know and are comfortable with, while still adding something that's a little different and exciting. She seemed to work well with the Doctor, and over the course of two episodes she was sympathetic enough that we were all pretty verklempt when she died.