I have nightmares at least four times a week, which really sucks, and the nightmare in question is usually the same. I can't prepare myself for having the nightmare before I go to sleep, either. Anyway...
In my dream, I "wake up" in my bedroom on the ceiling, with weird scuttling creatures everywhere - like spiders and rats combined. A ladder appears next to me, so I climb down the ladder towards the floor. Then the floor collapses, and the top of the ladder starts to disappear so I have to climb faster and faster, although I'm climbing upside down into a gigantic cave (where my floor used to be). Suddenly the ladder's rungs turn into giant snakes that wrap around my arms and throat. I'm getting suffocated while falling into a bottomless pit - which is fucking terrifying. Throughout the nightmare I keep getting visions of dead people, cats, and babies. A lot of the people that I see have been gruesomely killed, but even worse is that I've seen them (alive, of course) when I was awake that day. The dream ends with my neck breaking - either from hitting the ground or from the snakes - then I wake up.
Surprisingly enough, I don't get all that much sleep for fear of shitting my bed.