"Stick 'em up! I've got a gun!"
"Stick 'em up! I'm wearing a T-shirt with a picture of a cartoon-character holding a cartoon gun!"
I've been spared thus far, but both my poor wife and my poor daughter have had absurd experiences at the hands of airport security. I am 100% in favor of the concept, but I think political correctness and attendant nutcasedly skewed priorites have well-nigh vitiated effectiveness.