Now THAT'S a nightmare.

Husband's alarm went off, like it always does. I rolled over and saw him shut it off, then heard some kids running through the house yelling, "Fire!" Half-awake dreams involving kids are nothing new, three years working for SCOPE seems to have scarred me for life. But the yells of "fire" sparked a nagging fear, pun intended, and I tried to get Husband and say, "Please humor me and just make sure nothing's burning." He often humors my half-awake whims, mainly because I need him to - I don't give him peace until he does. But when I opened my mouth, nothing came out.
Still not alarmed (apart from the irrationally strong urge to make sure nothing was on fire), because I've been having sinus problems and was bound to wake up voiceless one of these mornings.
But then there was suddenly a man standing by Husband's side of the bed. Door to the room is on my side - he didn't come through it. He also didn't come through a window. He was just THERE. But he couldn't be. And while I was moving my mouth silently, trying to get Husband's attention and ask "Is there really a man there???" and failing because I couldn't talk or move, the man answered the question - he shook his head slowly. And smiled.
Hallucinations are a particular horror of mine. In grade-school I was prescribed a medication that has hallucinations as a side effect if you're allergic - which I apparently was. Saw very menacing furry little men and a lobster that varied between spaniel-size and pony-size. Saw them A LOT. "It can't really be there" is not a comforting thought, it's my worst nightmare.
I turned my head, and on my side of the room, there was a silent young woman in a long white nightgown. Okay, I've seen horror movies, I've seen most of "The Ring", and women in long white gowns better be real, talking, and not appearing in my bedroom. She laid down on the floor. And swam under my side of the bed.
I turned again to Husband, out of my head now, and he wasn't there. Someone else was. Or he was someone else, somehow. I looked back at the side of the bed - and the woman's very pale, very thin hands were clawing at the mattress by my feet.

I had a LOT of nightmares when I was younger, and I worked on conscious ways to make myself wake up. Even if your dream body has mobility, your real body doesn't, and forcing real movement will wake you up eventually if you can manage it, so I would try with all my might to blink my REAL eyes, really hard, again and again, or move my real lips, something. It feels profoundly strange, because once you get something moving, you feel like you have two bodies, the one in the dream and the one horizontal, trying its darndest to blink, and whatever you're really moving has practically no muscle behind it. And without even thinking about it, I was trying with everything I had, to move my hand. I realized I what I was doing when my fist started just barely tapping Husband's back. Just barely. My arm felt so dead that the effort actually hurt. Thankfully he felt it, and rolled over to ask, "Honey, are you okay?" which woke me up enough to gasp "NO I'M NOT!!!!"

That is THE most terrified I have been in a LONG time.