3. Martha Jones (Doctor Who)
Often unfairly marginalised as the weakest of the RTD-era regular companions, Martha Jones was seen by many fans as an unworthy successor to the very, very large hole that the departure of Rose Tyler left in many Doctor Who fans' hearts. After Rose departed, Russell T Davies introduced the regular character of Martha, a very strong departure from Rose - she was educated, a medical student and from a more affluent middle-class background than Rose's own working class origins. Martha, therefore, was bound to rub some fans of Rose the wrong way. She was equally brave and equally heroic but a lot of fans never warmed to her as much as Rose or subsequent companion Donna, despite a fantastic performance from Freema Agyeman. It's a real shame they didn't as Freema Agyeman gives a dazzling performance as a woman who is inquisitive, brave and intelligent, more than a match for the grieving Doctor who, sadly, barely acknowledges this until it's too late. Martha even saves the world on her own, going on a harrowing journey of survival around a devastated and crumbling Earth without any friends, any support and anything remotely resembling help, and survives to save the world. That's a hero by anyone's standards.