Episode 10 of the 4th season of House of Cards contains a fantastic scene of Frank intimidating Catherine Durant.
When referring to himself Frank initially uses first person singular:
But of course, it makes sense that they would've haunted me because it's all true.
-Everything Lucas Goodwin claimed. I killed them both, just like he said I did.
But then he switches to plural:
But of course, nobody believes it, and nobody ever will. Because that's how good we are at making things disappear. No, we didn't kill anybody. But we would have if it was necessary.
Who does he mean by "we"? The special forces that he is superior of? Some mysterious group of people behind him in existence of which he wants Catherine to believe? Him and Claire? Or maybe he's using pluralis majestatis to increase the impression?