Human Skull Fragments
You're on vacation in an exotic country and decide to pick up a souvenir made by local artisans. You don't speak whatever language they're speaking, so you point to an earthenware pot that looks like it would hold your umbrella collection. The shop owner makes the international sign for "No, no, no, that pot contains the remains of my dead grandmother!" but you think he's just playing hardball. You hand him a few extra greenbacks and grab the pot as you go.
You only realize your mistake when a TSA agent in Florida takes out the clay pot for further inspection and discovers that it indeed contains a well-preserved human skull. As usual, your wife was right; you should have just bought the "Hard Rock Cafe Turkmenistan" T-shirt.
Yes, TSA agents really did make this gruesome discovery in a checked baggage screening area at the Fort Lauderdale airport in 2013. The passenger claimed ignorance as to the pot's contents. This find naturally slowed down screening as the area turned into a crime scene [source: Burns].