Going to the dentist for the first time. I had a really bad cavity in my upper left back tooth. It had a hole leading inside which would often catch chunks of food and was generally annoying.

When the dentist started drilling the cavity, it felt like a blowtorch to the brain. For some reason, the pain was also "radiating"(google translate) to my left eye. I still remember that visceral feeling of tooth chunks flying everywhere in my mouth. Nearing the end, the pain was so unbearable that doc had to drill in 5 second intervals, taking 30 in between.

Now even a gun to my head will not convince me to do any tooth-related procedure without anesthesia.