A stupid traveler or someone looking for a free medical exam? Hmmm, my hospital charges about $2k for an X-ray. A plane ticket is only $300...

A friend of mine was returining from a honeymoon. His wife had purchased a large candle in a spherical glass container. When it went through the X-ray it looked like one of those cartoon bombs like you'd see Bugs Bunny use: big round ball with a string coming out of the top. Immediately security was all over the place, they were removed from line and their baggage searched. Everyone relaxed when they realized the bomb was just a candle.
The scary part is this: apparently airport security doesn't have a clue what a real bomb looks like. The round candle style things haven't been used for a good 150 years or so, and even then they were cannon balls made of iron and would look quite different on an Xray than a candle.