Compressed air.
I was once putting air in a car tire while on a road trip with a friend. After filling the last tire I handed him the tube and started screwing on the cap. For some dumb reason, he thought it would be funny to stick the air tube in my ear and turn it on.
I couldn’t hear out of that ear for like 20 minutes and it hurt so much. I probably should have gone to the hospital but the pain went away almost instantly and my hearing came back so I just didn’t go.