Knock-Knock

 is a unique weapon in Fallout: New Vegas. It is a unique variant of the fire axe.

Locations
Found in Camp Searchlight's Fire Station. Once you get the key from Logan, head upstairs and search the bathroom stalls, look in the right side corner of the stall with the Skeleton to find the Knock Knock.

Pop culture reference
Knock-knock refers to phrase said by dellusional writer Jack Torrance in Stanley Kubrick's classic "The Shining"(1980) whilst he is using a fire axe to break through a door.

"Knock-knock, here comes Johnny!!!!"

Appearances
appears in Fallout: New Vegas.