Another gotcha which I have seen twice is leaving the keys in the cabin door, and then forgetting about them. Completely fcuked the day of a Lear 45 pilot when the keys came out soon after take off and went straight through the port engine. Same thing happened to a friend, but he was luckier - the keys bounced off the nacelle and just got lost somewhere over the Sussex countryside.
ChubbyChopper
I have to admit to doing that in a Citation. Very Easy when there are two crew handling the Keys but the main Gotcha is that the door fixes back to the fuselage so if the key is in the lock you cannot see it.
I was lucky as after takeoff heard a funny noise, slowed right up and did a precautionary landing to check what the noise was.
Still could not see a problem until the door was reclosed and the handling agent noticed it from the outside.
The thing was spinning round like a prop in the airflow and yes it could head for the engine.
Now its added to the Checklist
Pace