Tonight I am revisiting an image I took a few years back with an Olympus Em-5. I was so impressed with the fact that it shot at an ISO of 25,600 that I immediately took it out for a test run.
You can probably tell, this was taken underground. Those are a couple of friends of mine rappelling into the cave from the topside. Yes, this was a pre-planned photo shoot, all I had to do was show up and crank the ISO up on my fancy new camera (at that time).
This was shot at ISO 10,000....not the 25, 600 that my camera advertised, but still way higher than I usually shoot and it still came out pretty dang cool...especially for that high an ISO number.