The worst flight I have had was a few months ago, going to Tunis. We were flying through a thunderstorm on approach, so it was getting a little bumpy.
The captain made a PA that the cabin crew should take their seats...
Needless to say, i put my seatbelt on straight away! I noticed a pax sitting in the seat opposite me, and he wasnt wearing his seatbelt! I told him to put it on, to which he replies: "Nahh... Im a frequent flyer, nothing ever happens!!"
Only a minute later the plane gets pushed down, and im forced against my seatbelt... (my crew idea is floating in front of my face) I see the man lift off his seat, and as the aircraft is suddenly pushed upwards again, he smashes down on the armrest. I have never heard a man scream so loud!! Turns out he broke his tailbone!!
So much for being a frequent flyer!