Investigators say the man took an unknown amount of cash from a 7-Eleven store Wednesday but left empty-handed when he tried to rob another store about 25 minutes later.
Police Lt. David Whitlock says no one was injured.
The StarTrek.com Web site says the double-pointed sword used by the Klingons on "Star Trek" is crescent-shaped and about a yard long. Police did not specify what material it was made of.
No one has been charged in the incident.