From Schneier on Security is a clever tip to have valuable things transported safely on planes.

A "weapons" is defined as a rifle, shotgun, pistol, airgun, and STARTER PISTOL. Yes, starter pistols - those little guns that fire blanks at track and swim meets - are considered weapons...and do NOT have to be registered in any state in the United States. I have a starter pistol for all my cases. All I have to do upon check-in is tell the airline ticket agent that I have a weapon to declare...I'm given a little card to sign, the card is put in the case, the case is given to a TSA official who takes my key and locks the case, and gives my key back to me. That's the procedure. The case is extra-tracked...TSA does not want to lose a weapons case. This reduces the chance of the case being lost to virtually zero. It's a great way to travel with camera gear...I've been doing this since Dec 2001 and have had no problems whatsoever.