Chinese glue gun small resistance
I did not know this, but apparently glue guns are made with rectangular** PTC (positive temperature coefficient) elements for the heater. From this source. 



Note that the resistance at room temperature should be much higher than you state (probably a couple hundred ohms depending on whether it's for 120 or 240VAC). Check your meter against a known value resistor just to be sure it is working correctly. 

** Okay, really a right-angled parallelepiped