I always flew with the armrests down and sat outboard because it made it difficult for the Captains to reach me and strike me in a sensitive area when it was my landing.
Later as a Captain I did the opposite and also purchased a long pointy stick.
I found the main threat as a copilot was the ability of the flight engineer to suddenly clip me from my six o'clock in the middle of the night with his meal tray. Apparently they do this if they have become bored and think the quiet dark cockpit needs a liven up.
He told me it was recommended in his SOPs that the F/E did this to the F/os around 03.00am local time on night flights...I of course believed him.