The scarriest I encountered was actually not the flight but the wait for it.

A couple of years ago I did a skiing trip from germany to Keystone, and on the flight back we were connecting in Detroit. We had only about 30 minutes to get to our other plane, so I just made a quick jump to the gate, with the other 40 germans slowly doing a sightseeingtrip in the airport (they will wait for us..and we have to buy liquor first anyway).
So arriving at the gate I expected to be rushed into the plane, but it was full of PAX, all waiting for the plane. After a couple of minutes me and another gentlemen asked one of the staff members what is, and we hitted the jackpot, the women all gave the information "we are waiting for the plane", he took us two to the side and told us, they would do a technical check on the plane, as they were unsure if it could fly another flight to germany that day. We would probably need to wait for the plane that arrives 2 hours later from Amsterdam.

So, everyone waiting forever, besides a few people all thinking the other plane just didnt arrive, when they finally announced boarding in 10 minutes. Me, the other guy and a few others who knew it too went to the friendly staff member and asked him what plane it was and he told us "they decided the plane could lift off for this flight"
You all know when those security annoucements come on? Everyone sleeps already? around 30 passengers listening very interested, looking for the next exit, how to use the lifevest! And the guy on the exit row made the flight attended explain for 5 minutes what to do in an emergency!
The flight itself was very shaky with turbolences, not a nice feeling. Cant recall having thanked the Captian so much for getting us savely to the ground!