A friend of mine was in the security line when he remembered he had some CO2 cartridges in his bag. They happened to be taped together so they wouldn't roll around. He pulled them out and tossed them in a trash can so he wouldn't have to deal with it when he got to the screeners.

Not suprisingly, a slight delay was created when a security officer saw someone toss several metal tubes wrapped in duct tape into a trashcan in a crowded section of a busy airport. He made his flight, but he had lots of explaining to do before he got there.