I'll get the ball rolling here...
Most of my fantasies are written on my blog, but not all of them.
I've had fantasies of robbing a bank because it's something I'd really like to do. I'd just like to do it for the thrill of it. The money would just be a bonus. It would be a huge risk and that's something that would excite me I think (I rarely experience excitement over anything). I probably never will rob a bank though, because the job I want to pull off would require a team effort.
I've also had mass murder fantasies.
Sometimes I like to go into the city and imagine killing everyone - man, woman and child alike - till all that's left is a pile of blood-soaked bodies. In that fantasy I am the lone survivor. I am God.
I've had a fantasy of going on a shooting spree and killing a bunch of cops. I die in that one - Suicide by cop. I'm not likely to ever fulfill that fantasy though, unless I felt like I had nothing left to lose.
I'm curious if others here have had similar fantasies to my own and why they had them.
In regard to nightmares...
I had a nightmare once that my mother was a serial killer. She was very cunning and calculating. She sent me down to the cellar to get more wine for our guests and that's when I knew I had become her target. I had a feeling she had set up a trap down there that would kill me. I woke up from the dream right before I walked into the cellar and thus, the trap.