I've found: krysyyjane9191 To be one. I sometimes watch it but not much because I forget xD Although I have it recorded on my Sky+ box in my room so I could watch it soon...
It's basically about the one surviving time lord who uses an old police box as a time machine and he goes back in time and fights monsters that are always conveniently ready to attack when he's there. He also has an assistant(s) usually. Oh, and he has an issue with guns, he never uses them.
so, if he's a monster slayer person thingy, why the hell is he called 'doctor' ? i don't usually watch tv shows, as i forget when they are on. lol
At first, I thought you were asking for a doctor who "fans" (I thought to be some unheard of medical procedure XD). Then I read the replies and it's about Doctor Who. I've never watched it before, but I've heard it's good.
Don't forget that he regenerates. I guess the same reason his enemy is "The Master"? I don't know either xD http://en.wikipedia.org/wiki/Doctor_(Doctor_Who)