Two stories. First one is kinda long and complicated. Feel free to ask me questions.
When I was in 1st grade I got really sick and was hospitalized. This wouldn't have been too big a deal (I had already been hospitalized a lot by that time because I had super severe asthma as a kid (still do, just not quite as bad) and would be hospitalized over a dozen more times because of it throughout my childhood) except my symptoms didn't correspond to a severe flu. Tests were ran, but were inconclusive. Since it could've been my appendix however I had an operation to have it removed (on a somewhat irrelevant note, finding out I'd have to have an appendectomy made me freak the fuck out because my sister had a computer game called Life & Death in which you played a surgeon, but she was terrible and always killed the patient, and it was always an appendectomy).
I had surgery and it turns out my appendix is completely healthy. My intestines are examined as well, but nothing appears to be abnormal. The surgeons aren't sure what else to do so they conclude the surgery. I continue to grow sicker. On top of my mystery illness, I develop pneumonia as a complication from the surgery and become sicker still.
It's worth noting at this point that I was given minimal pain medications after my appendectomy. I was in agony just laying in the bed. Movement was significantly worse, but I was not allowed medication that would actually lessen the pain and make it easier for me to move (and, you know, speed my recovery).
My pneumonia is treated and I recover from surgery but as none of the doctors can figure out what the fuck is wrong with me, they plan to airvac me to Denver to be examined there. My mom refuses to allow them to fly me there (damned if I know why) and insists she'll drive me to Denver in a few days (I really don't know why, it's a day away from Rapid City). The doctors agree for some reason, and in that time I actually grow considerably better. I still travel to Denver and am examined by multiple specialists, but none of them can diagnose me with any known illness. I made a full recovery, though to this day we still have no clue why I got sick, or how I recovered.
Oh well. At least I never have to worry about appendicitis. On a side note, I missed a literal month of school in the process.
Second story. Remember when I said I had super severe asthma? That's not an exaggeration. Colds, flu, allergies, exercise, excitement, and even laughter are triggers for me. When I was twelve I came down with a cold and asthma soon followed. It didn't seem as bad as other instances seeing as how I wasn't hospitalized, but that changed quite suddenly. At around midnight my asthma flares up. It hadn't been four hours since I had my medicine (asthma medicine ideally is administered every four hours or longer), but I was really having difficulties breathing so we use the medicine. Not only it fail to open my airways, I actually grew considerably worse. We tried again, but my condition continued to quickly deteriorate. I was gasping for air, and my lips were turning blue.
At this point, my mom realized I need to get to the ER immediately and called 911, which she had never done before. While mom is on the phone I became dizzy, lightheaded, and apparently drifted in and out of consciousness, because I have a hard time remembering the paramedics arriving at our house. Or the ride in the ambulance. Or arriving at the ER. Or being administered pure oxygen and a huge dose of asthma medicine. What I do remember is suddenly being properly aware I was in an ER bed, breathing oxygen and more asthma medicine. And I could breathe! I stayed in the ER for several hours (with oxygen the entire time) before, surprisingly, being cautiously discharged and allowed go home. After some days I got better and my asthma subsided.
As an adult my asthma isn't quite as bad as when I was a kid, but I do have the same triggers. So I always make sure to take my inhaler with me whenever I leave the house.
So, uh, there you have it. My two brushes with death. The tl;dr versions are 1) I had a severe, mysterious illness and doctors never found a diagnoses (and I had an appendectomy during the diagnoses process) but I spontaneously recovered and 2) I have horrible asthma and one time it almost killed me.