13. TARDIS Self Destruct Deception
Episode: Journey To The Centre Of The Tardis
Danger comes with the territory of being a companion. But the Doctor knows that, and his confidence (or ego) convinces him that he'll somehow save the day and keep his companions from harm. But when unexpected events occur that prevent that from happening, like a salvage ship's magnetic tractor beam breaking down the TARDIS, then we get a more desperate Time Lord.
With Clara trapped inside a TARDIS-turned-deathtrap, the Doctor activates the TARDIS' self-destruct in an attempt to enlist the salvage crew's help. Knowing he can't find Clara on his own, he basically traps the crew and threatens their lives unless she's found. It's later revealed that there really wasn't a self-destruct feature, and this was simply just another one of the Doctor's lies to get the job done.
But what's even more significant is that the Doctor uses fear to force the crew to save Clara's life, knowing full well that the brothers would be risking their lives as well. And had it not been for some unexpected timey-wimey involved later in the episode, the Doctor would have added to the list of those who have died for his cause.