The scariest things that have happened to me which were frightening at the time but worse later during the night when I woke up in a cold sweat at what might have happened was having a couple of near miss midair collisions.
First was climbing out at an airfield during type conversion familiarisation training and at 100ft hearing then seeing an RAF Phantom go underneath me, just above the tree tops. I immmediatley spun my head around to look for his wingman, who went just overhead me. After landing we rang Newcastle Radar to report it . They said they thought there had been a collision as they saw the dots coincide on the radar. We carried on flying for the rest of the day without really thinking much about it. When we got back in the evening the airfield operator told us the RAF pilots had rung up to apologise, they had been doing low level chasing and had drifted off course by 5 miles and cut through our circuit. I woke up in a cold sweat in the middle of that night.
The other time was on final approach to an airfield in a Twin Comanche when my wife yelled lookout and I saw the wheels of a Piper Arrow appear in my windscreen. I dived and banked away and went around for another go.
I was coming in on the normal approach slope and he had gone around the circuit and came in over the top of me without seeing me as I was below his line of sight. He was above me so I didn't see him either.
It didn't help that there were three training aircraft also in the circuit which was only air ground and when I called 2 ahead final to land, he though he was the second and I was behind him.
Didn't sleep much that night either.
Funnily enough when I had in flight problems I didn't have time to worry, just got on with the drills and they became non events.
Wheels stuck half down in the Twin Com on approach to Newcastle.
Complete Loss of Electrics in the Twin Com climbing out of Oxford through Brize.
Complete Loss of Electrics in a Robinson R44 just outside Gloucester.