A pen. Literally.
Source: https://pin.it/eocxvhuf6cbb2yOMG that is me.....i am that nurse.that thinks nothing about paging you in the middle of the night to return the pen you promised to give right back😷😂😂
I have also gone as far as to tell med students that my four color pen actually contains 3 colours and the fourth is filled with pancuronium that will stop them in their tracks if they leave the OR with my pen.😷😡