5. Benedict Cumberbatch
Cumberbatch's continued absence from Doctor Who is probably the most baffling quandry associated with the series since the big-time relaunch of the property in 2005. As the show has grown in profile once more, and taken America by storm in a way it never managed previously, it would have made effortless sense to cast one of the biggest rising stars in both TV and in Hollywood. Right now Cumberbatch may seem unattainable, given his considerably commitments - especially with Sherlock returning to screens, and roughly six hundred films in production with him in the lead (give or take a few) - but this sort of opportunity may well appeal to Cumberbatch's sense of Britishness (the same way Sherlock must surely have pulled on his patriotic strings.) Had he been born earlier, it is easy to imagine Cumberbatch as the third Gruber brother in some imagined Die Hard sequel, with the same stiff-lipped cool detachment making way for explosive moments of venomous emotion, and it is no accident that he finds himself on the same list as the other Grubers. The Valeyard ultimately has to carry the ultimate threat, if he is to be drawn as the ultimate Who villain, which would make sense, and Cumberbatch built on his dramatic presence in Star Trek Into Darkness to convince of his more imposing side. That too would add another facet to his potential take on the character.