I am standing behind a wall made of uranium.
I trapped the next user inside a radium box which I then buried ten kilometers underground.
I'm on another galaxy, where I'm on a very nice and tropical planet.
The next user is in a elevator that is stuck and is about to fall 100 floors to the ground, with no brakes.
However, the elevator was a very tight fit inside its shaft, so it slows down before it hits the bottom due to all of the air below it.
The next user is the plutonium core of a nuclear bomb at the moment of detonation.