One that sticks to mind when I was running the medbay was a doctor wearing an apron and a chef's hat trying to amputate a marine's right arm with a bayonet because he 'asked for a shiny new robot limb.' Upon questioning his usage of the bayonet, he complained that there were no other appropriate tools nearby while standing next to a surgical tray.
Another more light-hearted one was when I had the opportunity to IC mentor a player who clearly did not know the game's controls, leading to me spoonfeeding him rations while yelling at him to say that he was 'a slack-jawed baby who's too wet behind the ears to feed himself.' I think I later saw him playing normally so my advice worked somehow.