5. Lena Headey
Given that she's spent a lot of her career making waves in American television such as Terminator: The Sarah Connor Chronicles and the ever popular Game of Thrones, you'd be forgive for not realising that Headey was actually raised in Yorkshire, England. As such, a guest star role on Doctor Who would be a great way to bring a fantastic British performer back onto British TV. It'd also open her talents to a brand new audience as a lot of what she's done - *ahem* - isn't exactly what you could call family friendly. As for what she could play in Doctor Who, though... well, she's great at villains. She's been brilliantly vicious as baddies like Ma Ma in Dredd and Cersei Lannister in Thrones. A good antagonist always goes down a treat in a show like Doctor Who and Headey would create a stunning one for the Twelfth Doctor to battle. She can also do characters in more morally grey areas, who you're inclined to sympathise with, and out and out heroes like Sarah Connor. So there's a lot of scope there. Again, the experience with other fandoms wouldn't hurt either. She'd know what to expect from Who fans. Of course, she may well be busy with Game of Thrones and her film work. Then again, a guest stint wouldn't take long, so who knows?