Funny you should say that.

my latest thing is when I sit down on a flight I ask the person sat next to me "are you going to be using your sick bag at all? - It's just that I normally fill mine up on take-off"

Then sit back and enjoy the look on their face.

Mind you it does break the ice a little rather than sitting there for hours not looking at them.

Before the war on terror, if I saw an unattended package I used to think "I'll be having that!"