Scariest moment and "light bulb" moment are different for me.
Scariest moment was when we got called to a diabetic emergency in a dental clinic at 3 in the morning. Apparently the dentist who owned the clinic was a diabetic and had gone to check the clinic at 0300 after the burglar alarm had gone off. This was in response to a string of break ins that had occurred at his clinic where his narcotics had been stolen. Long story short, he was carrying a pistol and prepared to deal with anyone who was in the clinic. We show up at the request of his wife, who only gives us the half of the story about him being up there with low blood sugar, and go in to find him sitting down with a gun in hand asking "Who the f*** are you and why the hell are you here?" luckily the agency I was with at the time had a policy of always sending a PD escort, who was right behind us. We calmed him down, disarmed him, got his BG up and went on our way. It didn't really hit me until about 20 minutes later how close we really were to getting shot at.
I have been oa lot of good calls where myself and the crew really did a great job, but it was nothing another well trained crew could not have done. The one call so far in my career that i really feel stands out as a call where it was specifically me who made a difference was a few months back in the desert. We were called to intercept a BLS ambulance "with a baby." so I figured new born with low APGAR scores or some such thing...we never really got a lot of details working in Saudi. When we landed I found a full blown isolette in the back of the ambulance with a 36 week coarct baby, intubated with lines, hypoxic, sats in the 40's. Apparently the baby was being transported from Dammam to Riyadh (3 hours) and the ambulance had a crash, destroying the isolette's ventilator and disabling the pumps. The crew with the baby was a physician who had no idea how over his head he was, a nurse with a head injury (vomitting in the corner) and a RT with a broken arm. The baby was being BVM with 100% oxygen (very bad for ductal dependent heart defects) and hypoxic. Immediately my partner removed the oxygen and we were bagging in room air, I looked at the pumps and realized the PGE, sedation, and TPN were all not running, and had not been running for two hours. A bolus of PGE, a bit of sedation, removal of oxygen, and the baby looked great, sats in the upper 80's (great for a coarct.) all this while the doctor was yelling at me that I was killing the baby and he would not be responsible for the care I provided. Factor in that we were not going to be able to load the isolette in the helicopter, and I had to convince the ground crew to take me with them in the ambulance, and my partner and I were feeling pretty good when we arrived at the hospital.
I was really proud of this call because it required all the skills I have acquired over my short 7 years in EMS. it required me to be calm, make good decisions, and use what I have learned at the previous places I had worked. It also required me to make decisions and carry out patient care when I was the only one who knew what was going on, and with a physician yelling at me that I was about to kill a patient. It is one of the few calls where I know that i am one of the few paramedics around who could have ensured a positive patient outcome for that patient.
Sorry for being so long winded, I don't normally pat myself on the back...but since you asked...