One of the most hilarious was when I was stopped a couple of years ago for a pair of microscissors for microsurgery - the blades are about 5 millimeters (mm) long.....
No explanations would suffice, they had to go in my hold luggage. By the time I'd retrieved my bag and stowed the microscissors I'd missed the flight.
Dunno who I was supposed to threaten with those!
Ah well....