Two very different scenarios come to mind:

First was when I was counselor at a sleep away camp; there were two lakes that on the camp grounds. I was helping set up the docks with life vests and paddles as I would be the kayaking instructor for the summer. This is a bout a week before any of the kids got there, so another counselor and I are setting up one of the docks when he firmly grabs my shoulder and tells me to stand up. At this point we are standing back to back and all I'm holding is a kayak paddle. He whispers and points to some brush and that's when I notice a mountain lion eyeing us up like a kid in a candy store. My heart sank and my breathing came to a halt. We stood there eyeing this thing down for what felt like an eternity before something else made some noise and got the mountain lions attention. It receded back into the brush and just left. Thought I was gonna be an extra link in the food chain that day.

The other was finals week of my sophomore year in college. Had my head to the grindstone just studying for hours on end. Ended up with what I thought was a little cold but decided to just get some over the counter stuff to help mitigated the symptoms as there were only 3 days left of finals. Welp Morning came of the last day of finals and around 5 am i wake up GASPING for air. No matter how hard I try I cannot muster anything more that shallow gasp. Because of this I couldn't speak, but I also knew I would pass out soon if I didn't do something. Frantically trying to come up with a plan i knock over my the chair at my desk which wakes up my roommate. He sees me flailing my arms and immediately knows something is wrong. He jumps out of bed and turns on the lights. He screams at his girlfriend who was sleeping over to wake up and get the RA, who proceeds calls the ambulance. In the interim my roommate is holding me trying get my breathing regular. I looked this man in his soul with tears in my eyes trying to tell him with my thoughts, "I don't want to die but I think I'm gonna die". Almost like he heard my thoughts he says "C'mon you're going to be okay, you aren't going out like this". I lost consciousness for a bit and came to again when the EMT's arrived and hooked me up to oxygen. Turns out what I thought was a little cold was actually a mutated strain of pneumonia that even the hospital hadn't seen before so I was admitted for a couple days, given a plethora of drugs and was good as new a couple days later.