This was a deeply troubling dream. I don't know if I'd go so far as to call it a nightmare though, since it only took a dark turn near the end. 
The two of us were searching through a thrift store. Only it was large and ornate, like a Macy's or something. You'd expect there to be perfumes and fancy dresses but it was just row after row of typical thrift store junk. Then, something caught my eye.
It was a faded briefcase with flakes of the faux leather material coming off the edges. There was a combination lock, but it was busted. When I opened it up to look inside, there were two science fiction looking pistols. Like retro-futuristic, very "Buck Rogers" in appearance.
Next to the top one was a vial of enriched uranium. The included handbook said it was a radiation gun. When fired, it would pulverize a small amount of the uranium and then blast it in a cloud towards the target using compressed air. They would then die slowly of radiation poisoning over the next three days.
I opted not to purchase that one, certain that if it was real, I'd mess up with it and die of radiation poisoning. The second weapon was more interesting anyway. The handbook identified it as a deletion pistol but offered no instructions beyond those which apply generally to any sidearm (point away from self, keep safety on when not in use, etc.)
The radiation pistol was white ceramic and looked like a medical tool. The deletion pistol looked like a 1950s pulp scifi raygun. I didn't take it seriously because of that. It was only $15, so I bought it and took it to a Christmas party with me.
It was at my parent's house. There were all manner of elderly relatives who had already arrived. They'd set up a place for Amanda and I to get away from the bustle of the party, where we hung up our coats and took a breather. I took this opportunity to try out the deletion pistol.
I fired it absentmindedly at a wall. A glowing green spiral beam leapt from the barrel, impacting the wall harmlessly. I was astonished that it actually did something.I expected at most some flashing lights and sound effects, but not a visible beam!
I fired it at various objects until satisfied it apparently did nothing. Amanda joked that I should fire it at her, as a test. I did, satisfied it was just a fancy toy. The beam hit her and nothing happened. She laughed and said she was going to go rejoin the party.
The walked out of the room, leaving me to wonder who made this weird pistol and why. When I rejoined the party myself, I couldn't find Amanda. I asked if anybody had seen her and they all said no. I assumed she'd stepped outside or run to the store for something and shrugged it off.
My dad asked me about the old fashioned looking ray gun in my hands. I told him about how Amanda and I found it at a thrift store and that it actually shoots a visible, but harmless beam. To demonstrate I pointed it at him and fired it. The green glowing spiral beam struck him harmlessly in the chest.
He was surprised and delighted, asking to examine it. I walked over to give it to him, but before I could he vanished. No slow fade, no teleporter effect, he just abruptly disappeared. I would estimate it happened five full seconds after I'd shot him with the beam.
Everybody stared and got quiet. Why? Why was there a delay? That was infinitely worse than if it just instantly deleted you. A grey haired relative whose face I can't recall said "I think you ought to give me that pistol". I clutched it to my chest, realizing it was evidence. Possibly a murder weapon.
I ran away and searched for Amanda. Though by this point I already knew what had happened, I just didn't want to accept it. She wasn't in any of the rooms. She wasn't outside, though her car was. My options were rapidly dwindling to nothing.
A bunch of the party goers cornered me in the room that had been set up. My mother urged me to just hand it over. They rushed me, and reflexively I shot them all. They looked surprised, then fearful, then angry. They resumed rushing at me but disappeared a moment later, one after the next in the order I'd shot them.
My mother looked horrified and ran off. Soon after that I heard sirens in the distance, getting closer. So I turned the ray gun on myself and pulled the trigger. Then I sat there, alone in contemplation for the five seconds it took before I disappeared.
But I didn't die. I re-appeared about a mile away in the woods, with my Dad, Amanda, and the party goers I'd shot. Not a deletion pistol, then? A displacement pistol which just teleports the target to some pre-set distance away from you. They were all understandably angry with me however.
Stay Cozy!
