[quote=Imperfectionist]
I promise you, Wiki, unless you've got a Protonic Axe or a Ripper or something, you aren't going to be able to slit a power armored soldier's throat. It just ain't happening (as long as they're wearing the helmet).If an obvious target like the throat wasn't protected at least enough to repel knives, the armor wouldn't have made it past testing. In a nutshell, it's designed to protect the wearer in combat situation, including close combat, meaning knives =/= instant death. Not even close. In fact, looking at the image Sep used for the Royal Knight's , the shoulders and back of the armor are designed such that the only way to target the soldier's neck with a melee weapon is to come at them head-on AND at an awkward angle (i.e. you die)...There's a reason why it's so impressive, and so feared on the battlefield, you know. The best method to kill them, in my opinion, is to trick them into removing their helmets first, as otherwise there's pretty much no hope (except C4 or other very powerful explosives). Read the story of (the second leader of the Brotherhood of Steel) for a good example.
[/quote]

There weren't any power guards at the impreganation attempt of his sister. Plus its true you can't slit the throat of them but you can stab the neck. 

The helmet and the body armor are not connected (duh because how would they get in it otherwise :P), so the are small openings in the neck that a knife can easily get through.

I'm not saying that Power Guards are easy to kill but you can stab the neck with a knife. Of course due to their size and strength, it'd be a challenge but possible.