I think one of the worst ones I've had, or one of the most annoying ones persay, are the ones where you're trying to sleep in dream and "something" hovers over you and attempts to scream something.
Or ones where you're trying to do something to wake yourself up from the dream and it doesn't work right away
The one that I remember is from when I was young, maybe 10 or 12? My dad was driving home from work and made it to our street. For some reason, he ended up falling out of the truck, and it
ran over his legs.
That freaked me out for a long time and I had to make sure Dad was okay when he came home for a few weeks after that.
I know I’ve had some that are worse (including PTSD nightmares, unfortunately) but that’s one I remember that I’m actually willing to share.